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In This Report

•	Highlights
•	Introduction
•	Biological and Medical Caus...
•	Cultural and Emotional Caus...
•	Risk Factors
•	Complications
•	Weight Loss and Maintenance...
•	Weight Management
•	Medications
•	Other Treatments
•	Resources
•	References

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Weight control and diet

Highlights

Cancer and Weight Control:

• Cancer prevention guidelines from the American Cancer Society stress the importance of maintaining a healthy weight throughout life. A healthy weight is even more important than eating specific healthy foods, when it comes to cancer prevention.

Drug Warning:

• The US Food and Drug Administration (FDA) is warning consumers not to buy a product known as the "Brazilian diet pill." This product is labeled as a dietary supplement, but contains several chemicals found in powerful prescription drugs. The products are also known as Emagrece Sim and Herbathin dietary supplements.

New Over-the-Counter Medication:

• In February 2007, the FDA approved the first over-the-counter (OTC) weight-loss drug. Orlistat, previously available only by prescription as Xenical, will be available OTC at half its prescription strength. It will be sold under the name alli. Those eager to use the new pill should consider its cost and modest benefits compared with its side effects, most commonly oily diarrhea. This pill, which prevents fat absorption from food, also increases the risk of not absorbing important nutrients from food while using it. The FDA recommends taking a daily multivitamin supplement when using alli.

Research News:

• A small study in Norway found that a diet low in fat and high in carbohydrates ("carbs") increases symptoms of psychological distress, such as depression and anger. The study compared three different diets with varying amounts of fat and carbohydrates.
• A study released in March 2007 found that obesity in young girls results in early puberty -- as early as age 9.

Effects of Obesity on the Body:

• Obesity is associated with certain problems related to infertility, such as uterine fibroids or menstrual irregularities. In men, obesity can contribute to reduced testosterone levels.
• People who are obese are at higher risk for carpal tunnel syndrome and other problems involving nerves in their wrists and hands.
• The Pickwickian syndrome, named for an overweight character in a Dickens novel, occurs in severe obesity when lack of oxygen produces intense and chronic sleepiness and, eventually, heart failure.

Introduction

A stable weight depends on a good balance between the energy you get from food and the energy you use. You use energy during the day in three ways:

• As energy expended during rest (basal metabolism)
• As energy used to break down food (thermogenesis)
• As energy used during physical activity

Basal metabolism accounts for about two-thirds of spent energy. Your body generally uses this energy to keep your body temperature steady and keep the muscles of your heart and intestine working. Thermogenesis accounts for about 10% of spent energy.

When a person consumes more calories than the energy they use, the body stores the extra calories in fat cells. Fat cells function as energy reservoirs. They enlarge or shrink depending on how people use energy. If people do not balance energy input and output by eating right and exercising, fat can build up. This can lead to weight gain.

When energy input is equal to energy output, there is no expansion of fat cells (lipocytes) to accommodate excess. It is only when more calories are taken in than used that the extra fat is stored in the lipocytes and the person begins to accumulate fat.

Obesity is determined by measuring body fat, not just body weight. People might be over the weight limit for normal standards, but if they are very muscular with low body fat, they are not obese. Others might be normal or underweight, but still have excessive body fat. The following measurements and factors are used to determine whether or not a person is overweight to a degree that threatens their health:

• Body mass index (BMI) (a measure of body fat)
• Waist circumference (size around the waist)
• Waist-hip ratio
• Skin fold measurement (anthropometry)
• The presence or absence of other disease risk factors (e.g., smoking, high blood pressure, unhealthy cholesterol levels, diabetes, relatives with heart disease)

A person's disease risk factors plus BMI may be the most important components in determining health risks with weight.

The Body Mass Index (BMI). The current standard measurement for obesity is the body mass index (BMI). In general, a BMI of 25 - 29.9 means you are overweight. Obesity is a BMI of 30 and above. Obesity is then classified into three categories:

• Class 1: BMI of 30 - 34.9
• Class II: BMI 35 - 39.9
• Class III: BMI of 40 and greater

These guidelines are very important for people at risk for diabetes, heart disease, or certain cancers. It is also used to determine treatment approaches such as when surgery may be appropriate. The higher the BMI, the greater the risk for significant health problems.

Waist Circumference and Waist-Hip Ratio. The extent of abdominal fat can also be used in assessing risk of disease. Some studies suggest that:

• Women whose waistlines are over 31.5 inches and men whose waists measure over 37 inches should watch their weight.
• A waist size greater than 35 inches in women and 40 inches in men is associated with a higher risk for heart disease, diabetes, and impaired functioning.

Evidence strongly suggests that more body fat around the abdomen and hips (the apple-shape) is a more consistent predictor of heart problems and health risks than BMI.

The distribution of fat can be evaluated by dividing waist size by hip size. For example, a woman with a 30-inch waist and 40-inch hip circumference would have a ratio of 0.75; one with a 41-inch waist and 39-inch hips would have a ratio of 1.05. The lower the ratio the better. The risk of heart disease rises sharply for women with ratios above 0.8 and for men with ratios above 1.0.

Click the icon to see a depiction of the waist-to-hip ratio.

Anthropometry. Anthropometry is the measurement of skin fold thickness in different areas, particularly around the triceps, shoulder blades, and hips. This measurement is useful in determining how much weight is due to muscle or fat.

Biological and Medical Causes

Obesity results when a person consumes more calories than they need for the energy they use. Several different factors may influence weight gain.

About 90% of people who lose weight through dieting gain every pound back regardless of their weight-loss method.

Some evidence suggests that every person has an inherited weight. This range varies by only about 10% either up or down from some set point. For instance, a man whose "genetically-determined" weight is 200 pounds would tend to swing from 180 - 220 pounds. He would be unlikely to lose or gain more than this.

Genetic factors may play some part in 70 - 80% of obesity cases.

Appetite is determined by processes that occur both in the brain and gastrointestinal tract. Eating patterns are controlled by areas in the hypothalamus and pituitary glands (in the brain). The body produces a number of molecules that increases or decreases appetite. In some cases, the following factors may produce imbalances in this process:

• Insulin. Insulin is a hormone that helps change blood sugar (glucose) into energy. During digestion, carbohydrates from our diet break down into different types of sugar molecules (including glucose). Proteins from our diet break down into smaller molecules called amino acids. Immediately after eating, blood glucose levels rise. This triggers the release of insulin, which pours into the bloodstream. Insulin pushes the glucose and amino acids into cells and muscles. Insulin and other hormones determine which nutrients will be burned for energy or stored for future use. The inability to use insulin efficiently (insulin resistance) has been associated with both obesity and diabetes.
• Leptin. Leptin is a hormone that is released by fat cells. A number of scientists think this hormone may also be released by cells in the stomach. Leptin appears to play an important role in insulin resistance and fat storage in the body, but its role in obesity is unclear. The most likely scenario is that leptin levels rise as the cells store more fat. This increase in leptin levels decreases appetite. Falling levels of leptin make you feel hungry. In people who have genetically lower levels of leptin, however, the brain may be tricked into thinking that it is always starving because there is no leptin to decrease appetite. This can lead to weight gain.
• Resistin. Resistin is a hormone produced by fat cells. It makes the body resistant to insulin activity. Some experts believe it may help explain the role of obesity in diabetes type 2.
• Intestinal Chemicals. Ghrelin is a chemical produced in the stomach. It appears to be important in triggering the desire to eat. Peptide YY3–36 (PYY) is a substance secreted in the intestines after a meal. The level of PYY is proportionate to the number of calories a person eats. PYY tells the brain that you feel full. Deficiencies in ghrelin and PYY may contribute to some cases of obesity. Researchers are hoping that blocking ghrelin or infusing PYY may be possible treatments for obesity.
• Other Chemicals. Many brain chemicals are being studied for their role in appetite stimulation and weight gain. Among them are neuropeptide Y, melanocortins, agouti-related protein, and melanocyte stimulating hormone. Pain-relieving chemicals called endorphins may be critical in reducing appetite and regulating energy use. Cholecystokinin, a hormone released in the upper intestine that stimulates digestive juices, may work to control meal size.

Insulin is a hormone produced by the pancreas that is necessary for cells to be able to use blood sugar.

Genetics may directly contribute to severe obesity in people with family histories of the problem. Genetic factors such as slow metabolisms may also make people more likely to be overweight. At least seven genetic mutations have been associated with specific and uncommon cases of severe obesity. Some are outlined below.

• HOB1 (human obesity 1) is a gene that is linked to a high BMI in women.
• Leptin gene variants have been linked to leptin deficiencies and obesity.
• Melanocortin-4 receptor is a gene that helps turn off the urge to eat. It may not work properly in those with a family history of obesity.
• Researchers have also identified a mutation in a gene for a protein called proopiomelanocortin, which results in a syndrome of obesity, red hair, and deficiencies in stress hormones.
• A protein called agouti-related protein increases hunger. About 5% of severely obese people have mutations that over-respond to agouti-related protein.

Genetics also determine the number of fat cells a person has. Some people are simply born with more. It should be noted that even when genetic factors are present, a person can still control their diet.

The Thrifty Gene. Some experts think the existence of a so-called "thrifty" gene regulates changes in hormone levels, to accommodate seasonal changes. Theoretically, it works in the following manner:

• In certain populations, hormones are released during seasons when food supplies have traditionally been low. This leads to insulin resistance and increased fat storage.
• The process is reversed in seasons when food is readily available.
• Because modern industrialization has made high carbohydrate and fatty foods available all year long, the gene no longer serves a useful function. Fat, originally stored for famine situations, is not used.

This theory could explain why the previously nomadic Native American tribes who now have Western dietary habits have such high rates of Type 2 diabetes and obesity. In the past, the traditional low-fat, high-fiber foods tribe members ate may have protected them from obesity and type 2 diabetes. Today, these tribes' diet consists of more Western foods, which are higher in fat. Furthermore, these foods are readily available year-round, and many members of the tribe are sedentary. The result is a very high incidence of Type 2 diabetes and obesity. Although genetic abnormalities may make it harder or easier to lose weight, the occurrence of obesity has dramatically increased over the past two decades, and genes cannot have changed within that short amount of time. Our ability to use the food that we eat evolved so that our body could conserve energy and store fat during times of famine. Most cases of obesity now occur in people with normal body function who live in industrialized nations, where there is more than enough food.

A number of medical conditions may contribute to being overweight, but rarely are they a primary cause of obesity.

• Hypothyroidism is sometimes associated with weight gain. But, patients with an underactive thyroid generally show only a moderate weight increase of five to 10 pounds.
• Very rare genetic disorders, including Froehlich's syndrome in boys, Laurence-Moon-Biedl, and the Prader-Willi syndromes, cause obesity.
• Abnormalities or injury to the hypothalamus gland can cause hypothalamic obesity.
• Cushing's disease is a rare condition caused by high levels of steroid hormones. It results in obesity, a moon-shaped face, and muscle wasting.
• Obesity is also linked to polycystic ovarian syndrome, a hormonal disorder in women.

Click the icon to see an image of polycystic ovaries.

Some prescription medications contribute to weight gain, usually by increasing appetite. Such drugs include the following:

• Corticosteroids
• Female hormone treatments, including some oral birth control pills (effect is usually temporary), and certain progestins (such as Megestrol) used to treat cancer
• Antidepressants and anti-psychotic drugs, including lithium and valproate
• Insulin and insulin-stimulating drugs used to treat diabetes often lead to weight gain, a particularly unfortunate conflict of interest for obese individuals with type 2 diabetes

You should not stop taking any medications without your doctor's knowledge.

Cultural and Emotional Causes

Enough food is produced in the US to supply 3,800 calories every day to each man, woman, and child in the country, far more than the average person needs to sustain life. In a 2002 study, participants carefully recorded everything they ate and drank, and all activities and psychological factors surrounding the eating events. The people who gained weight ate more and their portions were larger than those who did not. This may be an obvious conclusion, but the public press often plays up biologic factors involved with obesity and overlooks the simple notion that Americans eat too much and exercise too little.

Obesity is dramatically increasing not only in American children and adults, but also in every country that has adopted similar cultural habits. The World Health Organization now considers obesity to be a global epidemic and a public health problem as more nations become "Westernized." In spite of the proven health risks of obesity, the government, insurance companies, and the medical profession do not spend nearly enough money to balance the commercial and cultural pressures that are producing millions of overweight people.

In 2007, the Robert Wood Johnson Foundation sounded a positive note with the announcement of a $500 million initiative, aimed at “reversing the childhood obesity epidemic by 2015.” The money will be used for research, education, and activities that promote healthy eating among America’s children.

Perhaps the primary reason for the dramatic rise in obesity is the sedentary (inactive) lives led by most Americans, including children and young people. In a 2003 study comparing modern life to the past, researchers found that labor saving devices had reduced a person's energy use by 111 calories a day -- adding up to an extra 11 pounds a year. Half the difference in energy use was due to less walking. At the same time, according to the U.S. Centers for Disease Control and Prevention, between 1970 and 2000 the typical American man increased his caloric intake by 168 calories a day (good for 17 pounds a year) while the average woman added 335 calories a day.

Regular television watching has been singled as the most hazardous pastime. According to a major 2003 study, for every 2 hours a person spends in front of the TV each day, the risk for obesity increases by 23% and for type 2 diabetes by 14%. In the study, TV watching produced the lowest metabolic rates compared to sewing, playing board games, reading, writing, and driving a car. Just the act of watching TV encourages unhealthy snacks and eating patterns. In addition, the advertising on the television complicates the problem by promoting fast foods, cereal, and snack products that are high in salt, fats, and carbohydrates. Even worse, much of these advertisements are directed at children -- the most vulnerable group.

People are not only eating more food than they did 20 years ago, they are also replacing home cooking with packaged foods, fast food, and dining out. This behavior, according to studies, places people at higher risk for obesity. Fast foods may be more harmful than restaurant cooking. These foods tend to be served in larger portions. They generally contain more calories and unhealthy fats, and less nutritious ingredients, than homemade or restaurant meals. Snack foods and sweet beverages, including juice and soft drinks, are specific problems that add to the increasing rates of obesity. Frequent small, healthy meals (instead of two or three large daily meals) have been associated with lower weights.

People react differently to stress. Some overeat and gain weight and others stop eating and lose weight. People who gain weight in response to stress often overeat foods high in sugar, fats, and salt. A 2003 study on rats suggested that stress hormones increase the pleasure of eating such so-called "comfort foods." Furthermore, the study supported previous research showing that stress-related eating was connected to the unhealthy accumulation of abdominal fat.

Risk Factors

Where you live plays a role in your risk for obesity. Simply living in the United States makes a person more susceptible to obesity. The prevalence of obesity in America has risen dramatically over the past few years and continues to increase.

• According to the latest figures available, 32.2% of American adults (aged 20 and older) are obese (BMI over 30) -- up from about 23% in the early 1990s.
• The number of Americans aged 20 - 74 who were overweight also increased -- from about 44.8% in 1960 to 65.2% in 2002.
• The rate of extreme obesity (BMI > 40) increased from 0.8% in 1960 to 4.9% in 2002.
• Obesity has increased in every state, in both men and women, across all age groups, and in every ethnic group, although some groups may face slightly higher risks than others.

Fat tends to settle in certain regions, depending on gender. Women gain fat predominantly in the stomach, hips and thighs, while men tend to gain fat in the belly and waist.

Risk by Age. People of any age are at risk for obesity. More children and adolescents are overweight in America than ever before. Gaining some weight is inevitable with age and adding about 10 pounds to a normal base weight over time is not harmful. The current weight gain in American adults over 50, however, is significant. By age 55, the average American has added nearly 40 pounds of fat during the course of adulthood. This condition is made worse by the fact that muscle and bone mass decrease with age.

Risk by Gender. In men, BMI tends to increase until age 50 and then it levels off. In women, weight tends to increase until age 70 before it plateaus. A 2000 study found that there are three high-risk periods for weight gain in women.

• The first is at the onset of menstruation, particularly if it is early. In fact, a study released in March 2007 found that obesity in young girls results in early puberty -- as early as age 9. This, in turn, increases the risk for more weight gain as girls enter puberty.
• The second is after pregnancy, with higher risk for women who are already overweight.
• Finally, many women gain weight after menopause.

These findings are significant because they may allow women to target high-risk times, and consequently prevent unnecessary weight gain.

Risk by Economic Group. Obesity is more prevalent in lower economic groups. One 2002 study reported that women who reported that they did not have enough food were more likely to be overweight than those who said they had sufficient food. Researchers discovered that the low-income women tended to have fewer fruits and vegetables but were actually taking in more calories a day than higher-income women. However, obesity is increasing in young adults with college education as well as in other groups.

Ethnic Groups. Among ethnic groups in general, African-American women are more overweight than Caucasian women but African-American men are less obese than Caucasian men. (Currently, 80% of African-American women are overweight.) Hispanic men and women tend to weigh more than Caucasians.

US Regions. Regionally, the prevalence of obesity is lowest in the Western states and highest in the South.

A number of dietary habits put people at risk for becoming overweight:

• Night-Eating Syndrome. Night-eating syndrome is defined as having no appetite in the morning, insomnia, and consuming more than half of daily food intake after 6:00 PM. It is associated with obesity and is difficult to treat. Stress reduction and relaxation techniques may be helpful.
• Binge Eating and Eating Disorders. About 30% of people who are obese are binge eaters who typically consume 5,000 - 15,000 calories in one sitting. To be diagnosed as a binge eater, a person has to binge at least twice a week for 6 months. Many experts believe that binge-eating carbohydrates causes an increase in a natural opiate leading to dependence on carbohydrates. Therefore, this condition should be treated as an addiction. Other eating disorders are bulimia and anorexia. Bulimia is binge eating followed by purging in order to lose weight. Anorexia nervosa is a mental illness in which the person refuses to maintain weight at the normal level. The patient with anorexia has a terrible fear of getting fat, and an abnormal perception of what his or her body looks like. Both conditions pose risks for serious medical problems, and anorexia nervosa can be life-threatening. A combined approach using behavioral therapy and antidepressants may help these individuals. [For more information, see In-Depth Report # 49, Eating disorders.]
• Restrained Eating. Some people, mostly middle-aged women who have normal weight, have a pattern referred to as restrained eating. This pattern requires a high level of conscious control and usually maintains a lower weight. However, such restraint places these individuals at higher risk for loss of control and subsequent overeating.
• Infrequent Eating. There is some evidence to suggest that eating small frequent meals uses more calories than infrequent large meals. It should be strongly noted, however, that packaged snack foods add calories and some do not produce a feeling of being full, so that people simply eat more than they should.

Anyone with Sedentary Lifestyles. Office workers, drivers, and anyone whose lifestyle involves sitting for long periods are at higher risk for obesity.

Ex-Smokers. The trend toward weight increase has followed the trend for quitting smoking. Nicotine increases the metabolic rate, and quitting, even without eating more, can cause weight gain, which may be considerable. It is important to note that weight control is not a valid reason to smoke. People in previous centuries did not smoke cigarettes, nor were they usually obese.

Shift-Workers. A recent study found that individuals who work late shifts (between 4 p.m. and 8 a.m.) tend to eat more and take longer naps than day workers and are more likely to gain excess weight.

People with Disabilities. Obesity rates are higher than average in people with physical or mental disabilities. Those with disabilities in the lower part of the body, such as the legs, are at highest risk.

Click the icon to see an image about TV watching.

Click the icon to see an image of childhood overweight.

Complications

General Adverse Effects of Obesity. Obesity, defined as a BMI of 30 or over, accounts for nearly 300,000 deaths in the U.S. each year. It is associated with more chronic health problems than smoking, heavy drinking, or poverty. Furthermore, given the current increase in obesity, it will surpass smoking as the most important preventable cause of death in America.

Some studies indicate the following health risks by body mass:

• The lowest risks for heart disease, diabetes, and some cancers are in people with BMI values of 21 - 25.
• The risks increase slightly when BMI values are between 25 - 27.
• The risks are significant in BMIs between 27 - 30.
• The same risks are dramatic at BMIs over 30.

Anyone with chronic health problems such as heart or lung disease, stroke, or arthritis, should be concerned about extra weight. This same concern also applies to people with known risk factors for such conditions.

• Metabolic Changes. As fat stores increase, the fat cells themselves enlarge and produce chemicals that increase the risk for several diseases. Such diseases may include diabetes, high blood pressure, gallbladder disease, and some cancers.
• Increased Mass. The increased body weight itself causes problems that result in injury and diseases, including osteoarthritis and sleep apnea.
• Harmful Fat Cell Types. Weight concentrated around the abdomen and in the upper part of the body (the apple shape) poses a higher health risk than fat that settles around the hips and flank (the pear shape). Fat cells in the upper part of the body appear to have different qualities from those found in the lower parts. In fact, studies suggest a higher risk for diabetes in people with the "apple shape" and lower risk in those who are "pear shaped."

Weight gain in the area of and above the waist (apple type) is more dangerous than weight gained around the hips and flank area (pear type). Fat cells in the upper body have different qualities than those found in hips and thighs.

General Adverse Effects of Being Overweight (Not Obese). It is still not clear if being overweight (a BMI of 25 - 29.9) hurts healthy people with no risk factors for serious illnesses.

According to one 2001 study, just being overweight increased the risk for developing diabetes, gallstones, hypertension, heart disease, stroke, and colon cancer. The risk rose according to how much the individuals were overweight. In any case, adults who are overweight in middle age face a poor quality of life as they age, with the quality declining the greater the weight. One study suggested, however, that being over 65 and overweight (but not obese) is not associated with higher mortality rates.

Some experts argue, in fact, that in anyone who is not severely obese, it is the unhealthy diet and sedentary lifestyle that causes harm -- not weight per se. In support of this argument, a British study found that overweight fit individuals had half the death rate of unfit trim individuals.

Being somewhat overweight may also have some benefits under specific circumstances:

• In older women, some excess fat may produce extra estrogen that helps slow down bone loss, and insulates bones from fall-related injuries. It should be strongly noted, however, that when older overweight women lose weight they report less pain, improved vitality, and improved physical function. The same positive effect of overweight does not appear to hold in older men.
• Conditioned athletes may have high BMIs because of very dense muscle tissue. Being fit in general may protect many overweight people.
• Some evidence suggests that Caucasians have the lowest mortality with BMIs of 24.3 - 24.7 while African-Americans are better off in the range of 26.8 - 27.1.
• Children may have higher normal fat levels during growth spurts and around puberty.

Individuals with a BMI of at least 30 have a 10 - 50% increased rate of death from all causes, compared with individuals with a BMI of 20 - 25. Mortality rates from many causes are higher in obese people, but heart disease is the primary cause of death. People who are obese have almost three times the risk for heart disease as people with normal weights. Being physically unfit adds to the risk.

Weight concentrated around the abdomen and in the upper part of the body (apple shape) is particularly associated with insulin resistance and diabetes, heart disease, high blood pressure, stroke, and unhealthy cholesterol levels. Fat that settles in a pear shape around the hips and lower body appears to have a lower association with these conditions.

Obesity poses many dangers to the heart and circulatory system.

Damage in the Blood Vessels. As people age, changes in body fat (particularly increasing abdominal fat) seem to cause stiffness in the aorta, the major blood vessel leading from the heart. Studies are finding higher levels of a factor called C-reactive protein (CRP) in people with obesity and abdominal fat. CRP is now considered to be a marker for inflammation and damage in the arteries. (Losing weight reduces CRP levels.)

High Blood Pressure. High blood pressure is the health problem most commonly associated with obesity, and the greater the weight, the greater the risk. High blood pressure carries serious risks of stroke, heart attack, and heart failure. The link between obesity and high blood pressure is complex, and may be a combination of genetic, population, and biological factors. Many studies have reported that modest weight loss is beneficial for reducing existing high blood pressure. [See In-Depth Report #14, High blood pressure.]

Heart Failure. An important 2002 study reported that obesity might account for 11% of heart failure cases in men and 14% in women. This link existed independently of other risk factors, such as high blood pressure, sleep apnea, and diabetes, which are also associated with obesity. The biologic mechanisms involved in obesity that lead specifically to heart failure are not clear. [See In-Depth Report #13, Heart failure.]

Unhealthy Cholesterol Levels and Lipid Levels. The effect of obesity on cholesterol levels is complex. Although obesity does not appear to be strongly associated with overall cholesterol levels, among obese individuals triglyceride levels (the major form of fat storage in the body) are usually high, while HDL levels (the "good" cholesterol) tend to be low. Both conditions are risk factors for heart disease. [See In-Depth Report #23, Cholesterol.]

Click the icon to see an image of coronary artery disease.

Stroke. Obesity is also associated with a higher risk for stroke. [See In-Depth Report #45, Stroke.]

Type 2 Diabetes and Insulin Resistance. Most people with type 2 diabetes are obese and, in fact, studies strongly suggest that weight loss may be the key in controlling the current epidemic of type 2 diabetes. The common factor appears to be insulin resistance. Insulin is a critical hormone in the use of sugar. In type 2 diabetes, different factors cause the body to become insulin resistant -- that is, the body can no longer respond properly to insulin. This has the effect of increasing sugar levels in the blood, the hallmark of diabetes. Both obesity and insulin resistance, at different phases, are marked by high levels of certain chemicals. It is not known yet if the higher levels are simply a product of obesity, or play some role in causing diabetes.

Insulin resistance is also associated with high blood pressure and abnormalities in blood clotting. Some research indicates that obesity, in fact, is the one common element linking insulin resistance, diabetes type 2, and high blood pressure. [See In-Depth Report #60, Diabetes - type 2.]

Metabolic Syndrome. Metabolic syndrome (also called syndrome X) is a pre-diabetic condition that is significantly associated with heart disease and higher mortality rates from all causes. The syndrome consists of obesity marked by abdominal fat, unhealthy cholesterol levels, high blood pressure, and insulin resistance. A 2002 study estimated that nearly a quarter of the U.S. population now has this condition. Even worse, according to a 2003 study, nearly a million American teenagers have this syndrome. A combination of weight loss and exercise is an effective treatment for this syndrome.

The American Cancer Society released new cancer prevention guidelines in September 2006. The guidelines stress the importance of keeping a healthy weight throughout life. The Society indicates that healthy weight is even more important than eating specific healthy foods, when it comes to cancer prevention.

Obesity has been associated with a higher risk for cancer in general and specific cancers in particular. Studies have also suggested that restricting calories reduces the risk for cancer. Some experts believe that effective weight control for children and adults could reduce cancer rates by 30 - 40%. One way obesity may increase the risk for cancer is its association with high levels of hormones called growth factors, which can trigger rapid cell production leading to cancer.

Uterine Cancers. The risk of uterine cancer in obese women appears to be two or three times higher than in thinner women.

Prostate Cancer. New studies from 2005 and 2006 report that obesity is associated with an increase in prostate cancer mortality, although not with the risk for less aggressive forms of prostate cancer.

Breast Cancer. Studies are mixed on the association between obesity and breast cancer. A number of studies have linked obesity to breast cancer in postmenopausal women, particularly in women who begin to gain weight after age 18.

Click the icon to see an illustrated series detailing a breast cancer surgery (mastectomy).

Gallbladder Cancer. Obese women are at higher risk for gallbladder cancer.

Gastrointestinal Cancers. A number of cancers in the gastrointestinal tract have been associated with obesity:

• Cancer of the esophagus may be due to a higher incidence of gastroesophageal reflux disorder (heartburn) in people who are overweight.
• Colon cancer has been linked to increased body mass in both men and women.
• Pancreatic cancer and obesity have been weakly linked, with one study reporting a lower risk in overweight people who are physically active.

Click the icon to see an illustrated series detailing a colon cancer surgery.

Muscles and Bones

Obesity places stress on bones and muscles. Studies report that the incidence of osteoarthritis is significantly increased in people who are overweight. People who are obese are also at higher risk for carpal tunnel syndrome and other problems involving nerves in their wrists and hands. It should be noted that some weight may be protective against osteoporosis (loss of bone thickness).

Obesity increases the risk for the following mouth and eye disorders:

• Gum disease
• Cataracts
• Maculopathy, an eye disease related to aging

Infertility. Abnormal amounts of body fat, either 10 - 15% too high or too low, can contribute to infertility in women. Obesity is specially related to certain infertility problems, such as uterine fibroids or menstrual irregularities. In men, obesity can contribute to reduced testosterone levels.

Effect on Pregnancy. Obesity has many dangerous effects on pregnancy. These include high blood pressure, gestational diabetes (diabetes, usually temporary, that occurs during pregnancy), urinary tract infections, blood clots, prolonged labor, and higher fetal death rate in late stages of pregnancy. Obesity is also associated with increased rates of cesarean delivery. Infants of women who are obese are also at higher risk for neural tube birth defects, which affect the brain or spine. Folic acid supplements, ordinarily effective in preventing these conditions, may not be as protective in overweight women.

Obesity is thought to be a risk factor for symptoms of adult-onset asthma. Though there is evidence that obesity causes wheezing and shortness of breath, it does not appear to be strongly associated with the disease mechanisms in the lungs that cause true asthma.

Obesity also puts people at risk for hypoxia, a condition in which there is not enough oxygen to meet the body's needs. Obese people need to work harder to breathe. They tend to have breathing muscles and lungs that do not work as well as those in thinner people.

The Pickwickian syndrome, named for an overweight character in a Dickens novel, occurs in severe obesity when lack of oxygen produces intense and chronic sleepiness and, eventually, heart failure.

Nonalcoholic Fatty Liver Disease. People with obesity, particularly if they also have type 2 diabetes, are at higher risk for a condition called nonalcoholic fatty liver disease, also called nonalcoholic steatohepatitis (NASH). This condition causes liver damage that is similar to liver injury seen in alcoholism. In some cases, it can be very serious and require liver transplantation. It occurs in about half of people with diabetes, and 20 - 50% of obese people, depending on how severe their obesity is. NASH can also occur in overweight children.

Gallstones. The incidence of gallstones is significantly higher in obese women and men. The risk for stone formation is also high if a person loses weight too quickly. In people on ultra-low calorie diets, gallstones may be prevented by taking ursodeoxycholic acid (Actigall).

Click the icon to see an image of gallstones.

People who are obese and nap tend to fall asleep faster and sleep longer during the day. At night, however, it takes them longer to fall asleep, and they sleep less than people with normal weights. In an apparent vicious circle, studies have suggested that obesity not only interferes with sleep but that sleep problems may actually contribute to obesity.

Sleep Apnea. Obesity, particularly the apple shape, is strongly associated with sleep apnea, which occurs when the upper throat relaxes and collapses from time to time during sleep. This collapse temporarily blocks the passage of air. Sleep apnea is increasingly being viewed as a potentially serious health problem, which may lead to complications such as heart disease and stroke. Some studies suggest that among overweight people, those who have sleep apnea have a greater risk of heart disease than those without it. In one study, the more obese a person with sleep apnea was, the higher the pressure on the airway, and therefore the greater the obstruction of the airway. Obstructive sleep apnea may also add to obesity, however, as sleepy people tend to be sedentary. Some studies indicate that treating sleep apnea may help people lose abdominal fat.

Narcolepsy. A small European study found a link between narcolepsy (a sleep disorder characterized by excessive daytime sleepiness with frequent daily sleep attacks) and high BMI.

Depression. A number of studies have reported an association between depression and obesity, particularly in obese women. There may be a number of factors to explain the link. In some cases of atypical depression, people overeat and may gain weight. Overweight people may also become depressed because of social problems and a poor self-image. In these cases, depression usually disappears when people lose weight.

There is evidence, however, that obesity itself may impair levels of tryptophan -- a chemical needed to make serotonin, a brain chemical associated with mental well-being. In one study, even after people lost weight, tryptophan levels were lower than normal.

There does not appear to be any association between depression and obesity in men.

Social Problems. One long-term study reported that overweight young women completed fewer years of school, were 20% less likely to be married, and had 10% higher rates of household poverty than their thinner peer. Obese young men were also less likely to be married, and their incomes were lower than their thinner peers. Nevertheless, studies consistently show that overweight males (both boys and men) are not as severely emotionally affected as females of any age. Women and girls tend to blame themselves for being heavy, while males tend to blame being overweight on outside factors.

Weight Loss and Maintenance

Even modest weight loss can reduce the risk factors for heart disease and diabetes. The simplest (but still difficult) approach to weight loss is reducing calories and exercising at least 150 minutes a week. Behavioral and mental changes in eating habits, physical activity, and attitudes about food and weight are also essential to weight management. For people who are very overweight and cannot lose weight through lifestyle changes, a number of effective weight-loss medications are available. For those with severe obesity, surgical procedures are proving to be very beneficial.

Some Tips for Losing Weight. The following are some general suggestions for dieters:

• Start with realistic goals. Diet failure is extremely common, and the odds of significant weight loss are low, particularly in people with the highest weights. People who are able to restrict calories, engage in an exercise program, and get help in making behavioral changes can expect to lose between 5 - 10% of their current body weight. That is generally all that is needed to achieve meaningful health changes. Certainly, the distorted image of a super-thin female shape should not be anyone's goal.
• Maintain a regular exercise program, assuming you have no health problems that will stop you. Choose a program that you enjoy. Check with your doctor about any health considerations. [See In-Depth Report #29 Exercise.]
• Do not use hunger pangs as cues to eat. A stomach that has been stretched by large meals will continue to signal hunger for large amounts of food until its size reduces over time with smaller meals.
• Be honest about how much you eat and start by recording all calories in writing. Studies suggest that when many people report their own calories intake they significantly underestimate their consumption of high-calorie and over-estimate the low-calorie foods. People who do not carefully note everything they eat tend to take in too many calories when they believe they are dieting.
• Observe weekend eating. People tend to eat more on the weekends. If it is difficult to monitor all meals during the week, it be may be useful to at least track eating habits during the weekends.
• Once the pounds are lost, do your best to keep the healthier weight. Make daily, even hourly, conscious decisions about eating and exercising activities. Such thinking, in many cases, can become automatic and not painful.
• Don't give up, even after repeated weight loss failures. Most studies indicate that yo-yo dieting or weight cycling have no bad psychological or physical effects. Repeated dieting also does not harm the body's ability to burn calories efficiently.
• Weight loss, in any case, should not be the only or even the primary goal for people concerned about their health. The success of weight loss efforts should be evaluated according to improvements in disease risk factors or symptoms, and by the adoption of healthy lifestyle habits, not just by the number of pounds lost.

Weight Management

There are many approaches to dieting and many claims for great success with various fad diets. To date, although many diets achieve effective immediate weight loss, none has emerged as an effective tool for maintaining healthy weight. The only definite recommendation that can be made about any diet plan is to be sure it includes an exercise program, assuming there are no health problems to forbid it.

The original food pyramid, with four food groups, has been replaced with an updated food guide called "My Pyramid." This illustrates the relative proportions of different foods that make up a nutritious, well-balanced diet and includes exercise.

Calorie restriction has been the cornerstone of obesity treatment. The standard dietary recommendations for losing weight are the following:

• As a rough rule of thumb, one pound of fat equals about 3,500 calories. A person could lose a pound a week by reducing daily caloric intake by about 500 calories a day. Naturally, the more severe the daily calorie restriction, the faster the weight loss. Very-low calorie diets have also been associated with better success, but extreme diets can have some serious health consequences.
• To determine your daily calories requirements, multiply the number of pounds of ideal weight by 12 - 15 calories. The number of calories per pound depends on gender, age, and activity levels. For instance, a 50-year old woman who wants to maintain a weight of 135 pounds and is mildly active might require only 12 calories per pound (1,620 calories a day). A 25-year old female athlete who wants to maintain the same weight might require 25 calories per pound 2,025 (calories a day).
• Fat intake should be no more than 30% of total calories. Most fats should be in the form of monounsaturated fats (such as olive oil). Saturated fats (found in animal products) should be avoided.

This dietary approach requires counting only grams of fat with the goal of achieving 30% or fewer calories from fat. One gram of fat contains nine calories, while one gram of carbohydrates or protein has only four calories. Fat in your diet converts more readily to fat in the body, compared with carbohydrates or proteins. Simply switching to low-fat or skimmed dairy products may be enough for some people.

There are possible drawbacks to this approach:

• Some people who reduce their fat intake may not get enough basic nutrients, including vitamins A and E, folic acid, calcium, iron, and zinc. People on low-fat diets should eat a wide variety of foods and take a multivitamin supplement, if appropriate. Calcium deficiencies may be particularly harmful in women at risk for osteoporosis.
• Many people start eating foods with too many carbohydrates, believing that they are not adding calories. No one should use a low-fat diet as an excuse for eating too many carbohydrates, particularly starchy foods and sugar. A high-calorie diet from any source will add pounds.
• A small study in Norway found that a diet low in fat and high in carbohydrates ("carbs") increases symptoms of psychological distress, such as depression and anger. The study compared three different diets that had varying amounts of fat and carbohydrates in each. The diets contained the same amount of calories, but differed in the percentage and type of fat. People on the low-fat, high-carbohydrate diet reported more anger and depression compared with the other two diets.
• Replacing fatty foods, such as cakes, cookies, and chips, with their commercial "low-fat" counterparts does not constitute a low-fat diet. These foods generally contain more sugar and hence calories, not to mention other ingredients, which have virtually no nutritional value. In fact, a 2002 study suggested that increasing sugar may, over time, reduce levels of HDL ("good") cholesterol.
• Very low-fat diets may increase the risk for stroke from hemorrhage in the brain.

Some fat in a diet is essential. It should come from plant oils and fish, however, and not from animal products or hardened oils, such as margarine. Trans-fatty acids, found in hardened oils, are actually more of a risk factor for obesity than saturated fats from animal products, although both should be avoided.

Fiber and Complex Carbohydrates. In all cases, complex carbohydrates found in whole grains and vegetables are preferred over those found in starch-heavy foods, such as pastas, white-flour products, and potatoes. Fiber is an important component of many complex carbohydrates. Fiber is almost always found only in plants, particularly vegetables, fruits, whole grains, nuts, and legumes (beans and peas). One exception is chitosan, a dietary fiber made from shellfish skeletons. Fiber cannot be digested but passes through the intestines, drawing water with it, and is eliminated as part of feces content. The following are specific advantages from high-fiber diets (up to 55 grams a day):

• Insoluble fiber (found in wheat bran, whole grains, seeds, nuts, and fruit and vegetable peels) has been associated with weight loss. Studies also suggest that diets rich in fiber from whole grains reduce the risk for type 2 diabetes.
• Soluble fiber (found in dried beans, oat bran, barley, apples, citrus fruits, and potatoes) has important benefits for the heart, particularly for achieving healthy cholesterol levels and possibly benefiting blood pressure as well. Simply adding breakfast cereal to a diet appears to reduce cholesterol levels. People who increase their levels of soluble fiber should also increase water and fluid intake.

High-protein, low carbohydrate diets, such as the Atkins and South Beach diets, have been touted as effective ways to produce short-term weight loss. Because of their emphasis on fats and proteins, many experts are concerned about long-term health problems. A report in the March 2006 Lancet linked the Atkins diet to life-threatening complications that caused the death of one woman. The 40-year-old woman had a deadly buildup of acids called ketones in her blood, a condition called ketoacidosis. Ketoacidosis can cause coma and death. Ketones are a known by-product of high protein, low carbohydrate diets. At low levels they can cause nausea, lightheadedness, and bad breath.

The long-term effects of these diets are still unknown. For example, the Atkins diet restricts some vegetables and most fruits, which are known to protect against serious diseases such as heart problems and cancer. The diet may also cause too much calcium to build up in the urine. This can increase the risk for kidney stones and osteoporosis. In addition, high-protein intake, particularly from meat, can be harmful in people with kidney problems. Individuals at risk for kidney stones, or those who have other kidney problems, should not go on high-protein diets without talking to their doctor first. Unfortunately, many people with diabetes are at risk of kidney problems, which could reverse any possible benefits a high-protein diet may bring them. Eating a lot of meat has also been associated with certain common cancers, notably prostate and colon cancers. A 2002 study suggested that such diets during pregnancy may increase the risk for high blood pressure in the child.

Still, significant studies say that such diets improve cholesterol and blood sugar levels. Studies in 2002 and 2003 have indicated that these diets lower blood glucose levels, which can be important in people who are diabetic. The diets also reduce triglyceride levels (unhealthy fat molecules) and increases HDL (" good") cholesterol levels. High triglyceride and low HDL levels are important risk factors for heart disease, and are common in people with type 2 diabetes. Studies are mixed on whether this type of diet reduces overall cholesterol or LDL ("bad") cholesterol levels.

Experts that promote the low carbohydrate approach argue that heart problems from obesity are due to insulin disturbances from sugar imbalances. Therefore, they believe that restricting carbohydrates is the best approach for obesity -- especially for overweight people with diabetes. More research is needed, however, to determine the long-term impact of such diets on health.

High-protein, low-carbohydrate diets include Atkins, Protein Power, Sugar Busters, and Dr. Stillman. The Atkins diet is one of the most popular and has a four-phase program:

• Induction. For the first 2 weeks, individuals consume no more than 20 grams of carbohydrates a day. The diet consists of pure protein and fats. There is no fruit, bread, grains, starchy vegetables, or dairy products other than cheese, cream, or butter. This phase is not suitable for children, pregnant women, or anyone with kidney disease.
• On-going Weight Loss. After the first phase, individuals continue to lose weight while they increase carbohydrate levels by five grams each day.
• Premaintenance. When individuals get close to their weight goal, they add another 10 grams of carbohydrates per day as long as they do not begin to gain weight. Weight loss is very slow at this time, but the individual is now getting used to maintenance.
• Maintenance. Lifetime maintenance is usually between 40 and 100 grams of carbohydrates a day, depending on steady weight level.

Anyone who chooses this diet should prefer fish or soy products to meat as protein sources. Fish may reduce leptin, a hormone associated with fat storage and heart diseases, and would be the best protein source. People on this diet should also choose monounsaturated fats (as in olive oil) over saturated fats or trans-fatty acids fat. Patients often need supplements, at least a multivitamin and possibly calcium, chromium, omega-3 fatty acids (found in fish oil), and other supplements.

The South Beach and Zone diets encourage healthy fats. They also allow certain carbohydrates. For example the Zone uses healthy carbohydrates (vegetables and dried beans) and unsaturated fats. The South Beach diet uses carbohydrates that have a lower impact on blood sugar levels. This is called a low-glycemic index. Low-glycemic foods include barley, dried bean and peas, milk, strawberries, and apples. High-glycemic foods include refined grains, white bread, white potatoes, and bananas and other tropical fruits. The glycemic index was developed for use in diabetes -- not for weight loss. Nevertheless, there is some evidence that foods with low glycemic indexes may produce a feeling of fullness and so discourage further eating. As with any high-protein diets, people at risk for kidney stones, or those who have other kidney problems, should avoid these plans.

Some studies have reported good success with meal replacement beverages (Slim-Fast, Sweet Success). They contain major nutrients needed for daily requirements. Each serving typically contains between 200 - 250 calories and replaces one meal. (Note: Using them for all meals reduces calories to a severe extent and can be harmful.)

One study reported that most subjects who had undergone a 12-week weight loss program and then used Ultra Slim Fast supplements as directed for maintenance kept off more than half their weight loss after more than 3 years. A quarter of the subjects were still losing weight.

Medical evidence suggests that a diet rich in magnesium could reduce a person's risk of metabolic syndrome, a cluster of problems including obesity, high blood pressure, and high cholesterol. Metabolic syndrome can lead to diabetes and heart disease. A long-term study of thousands of Americans found that the risk for metabolic syndrome decreased in those who consumed the most magnesium from meals. The findings were published in the journal Circulation.

Commercial and Non-Profit Support Programs for Weight Loss. There are many different types of weight-loss program. (This report cannot address all of the many commercial and nonprofit weight-loss programs currently available, nor can it assess their claims.)

Taking off Pounds Sensibly (TOPS), a nonprofit support organization with many local chapters, is one of the least expensive programs, costing $20 a year.

Most of the commercial programs such as Weight Watchers, Jenny Craig, and NutriSystem offer individual or group support, lifestyle changes and packaged meals. These programs tend to be expensive. There are few well-conducted studies on these programs. One 2003 study reported modest weight loss over 2 years with Weight Watchers compared to a self-help program. There were no differences in heart risk factors.

Cognitive Behavioral Approaches. Most support programs use some form of cognitive-behavioral methods to change the daily patterns associated with eating. They are very useful for preventing relapse after initial weight loss. The following is a typical approach:

• The patient first records in a diary all activity related to eating patterns, including the times of day, length of meal, emotional states, companions, and, of course, the kind and amounts of food eaten. Most people -- even professional dieticians, according to one study -- tend to underreport their daily calorie intake. However, writing it down is still a good method for increasing a person's awareness of eating patterns. (One patient said that recording circumstances surrounding relapses was a particularly valuable guide for understanding the stresses leading to her own eating behaviors.)
• The patient reviews the diary with a therapist or group to set realistic goals and identify patterns that the patient can change. For instance, if food is normally eaten while watching television, then the patient may be advised to eat in another room instead.
• Good eating habits are reinforced by rewards. These rewards are other pleasures that substitute the high calorie consumption and sedentary activities.

Behavioral modification has been shown to be helpful particularly for people who have an overly strong response to the taste, smell, and appearance of food. It also may be useful for binge eaters.

Stress-Reduction Techniques. Stress reduction and relaxation techniques may be helpful for some people with obesity, such as those whose weight is related to night-eating syndrome. [See In-Depth Report #31, Stress.]

Changing Sedentary Habits. Making even small changes in physical activity can expend energy. For example, simply getting up to turn the TV on and off instead of using the remote, and standing (instead of sitting) while talking on the phone may help a person lose up to five pounds a year. Other suggestions include cooking one's own food (instead of eating take-out or fast food), walking to as many places as possible, using stairs instead of escalators or elevators, and gardening. Even fidgeting may be helpful in keeping pounds off, and, in one study, chewing gum increased energy expenditure.

No one should rely on such mild activities, however, for serious weight loss. Only high levels of physical activity -- not just using up energy -- help prevent obesity.

Approach to Exercise. Exercise, which replaces fat with muscle, is the critical companion for any weight control program. In a one-year study, women who regularly averaged 3.5 days (176 minutes) of exercise each week lost significantly more weight than women who did not exercise regularly. Women who exercised more than 195 minutes a week lost nearly 7% of their abdominal fat.

People who exercise are more apt to stay on a diet plan. Exercise improves psychological well-being and replaces sedentary habits that usually lead to snacking. Exercise may even act as a mild appetite suppressant. Moreover, exercise improves overall health even with modest weight loss. In support of this, a British study found that overweight fit individuals had half the death rate of unfit trim individuals.

Be aware, however, that the pounds won't melt off magically. Losing significant weight requires both intensive exercise and calorie restriction. In addition, if a person exercises but doesn't diet, any actual pounds lost may be minimal, because denser and heavier muscle mass replaces fat. Nonetheless, regardless of weight loss, a fit body will look more toned and be healthier. In addition, exercise benefits the heart even with modest weight loss.

The following are some suggestions and observations on exercise and weight loss:

• The more strenuous the exercise, the better the chances for short-term and long-term success. With intense exercise, the metabolism continues to burn calories before returning to its resting level. This state of elevated metabolism can last for as little as a few minutes after light exercise to as long as several hours after prolonged or heavy exercise.
• Of the standard aerobic machines, the treadmill burns the most calories. It may be particularly effective when used in short multiple bouts during the day. In fact, frequent exercise sessions as short as 10 minutes in duration (about four times a day) may be the most successful exercise program for obese people.
• Resistance, or strength, training is excellent for replacing fat with muscles. It should be performed two or three times a week.
• As people slim down, their initial level of physical activity becomes easier and they burn fewer calories per mile of walking or jogging. The rate of weight loss slows down, sometimes discouragingly so, after an initial dramatic head start using diet and exercise combinations. People should be aware of this phenomenon and keep adding to their daily exercise program.
• As people age, they also need to exercise more to keep off the same amount of weight.
• Changes in fat and muscle distribution may differ between men and women as they exercise. Men tend to lose abdominal fat (which lowers their risk for heart disease faster than reducing general body fat). Exercise, however, does not appear to have the same effect on weight distribution in women. In one interesting study, women in aerobic and strength training programs lost fat in their arms and trunk, but did not gain muscle tissue in these regions.

Warning Note. Because obesity is one of the risk factors for heart disease and diabetes, anyone who is overweight must discuss their exercise program with a doctor before starting. Sudden demanding exercise, in such cases, can be very dangerous. [See In-Depth Report #29, Exercise.]

Medications

There are several different drugs used for weight loss. Unless specifically instructed by a doctor, people should use non-drug methods for losing weight. Except under rare circumstances, pregnant or nursing women should never take diet medications of any sort, including herbal and over-the-counter remedies.

A 2001 study reported that 7% of American adults use nonprescription weight-loss products. People must be cautious when using any weight-loss medications, including over-the counter diet pills and herbal or so-called natural remedies. Buying unverified products over the Internet can be particularly dangerous.

Green tea. Perhaps the best alternative advice for people who are overweight is to drink tea. Studies have indicated that regular tea drinking is associated with lower weight, particularly in people who drink it for years. Green tea specifically has been associated with increased energy expenditure. One study reported that people who took a green tea extract (Exolise) lost weight and reduced their waist size. Better evidence is needed to confirm the results on this supplement.

Thermogenic Approach to Weight Loss. An approach to weight loss called thermogenic (also hepatothermic) therapy is based on the idea that certain natural compounds have properties that enable the liver to increase energy in the cells and stimulate the metabolism. Theoretically, the result would be fat loss. Among the natural substances used in such products are EPA-rich fish oil, sesamin, hydroxycitrate, pantethine, L-carnitine, pyruvate, aloe vera, aspartate, chromium, coenzyme Q10, green tea polyphenols, aloe vera, DHEA derivatives, cilostazol, diazoxide, and fibrate drugs.

Nearly all the current over-the-counter dietary aids contain some combination of these ingredients. There is no evidence that any of these ingredients can produce weight loss, and some may even have harmful effects.

Chromium is a common ingredient in many diet supplements (e.g., Xenadrine, Dexatrim, Acutrim Natural, Twinlab Diet Fuel). It is claimed to specifically promote fat loss, rather than lean muscle loss. Some evidence suggests that niacin-bound chromium may improve insulin sensitivity. On the negative side, animal studies have suggested that chromium may have damaging effects on genetic materials in cells. This could cause sterility.

Orlistat (Xenical) can help about one-third of obese patients with modest weight loss, and can assist in long-term maintenance of weight loss. It works by slowing the absorption of fat (by about 30%) in the intestine. Studies indicate that between 50 - 80% of patients can achieve weight loss of 5% or greater, depending on other lifestyle changes. However, many people regain a significant portion of this weight back within 2 years. It does not work for all patients, however. In one survey of patients who took it, 10% gained weight or did not lose any, and 43% lost less than 5%. Nevertheless, orlistat may delay or even prevent the onset or progression of diabetes and improve cholesterol levels, regardless of weight loss.

The drug can cause gastrointestinal problems and may interfere with absorption of the fat-soluble vitamins A, D, and E and other important nutrients. The most unpleasant side effect is oily leakage of feces from the anus. Restricting fats can reduce this effect. People with bowel disease should probably avoid it. In spite of these side effects, most patients are able to tolerate this agent.

In February 2007, the FDA approved an over-the-counter (OTC) version of orlistat. It will be sold under the name alli, and will be available at half the prescription strength of Xenical. Those eager to use the new pill should consider its cost and modest benefits compared with its side effects, most commonly oily diarrhea. This pill, which prevents fat absorption from food, also increases the risk of not absorbing important nutrients from food while using it. The FDA recommends taking a daily multivitamin supplement when using alli.

Sibutramine (Meridia) helps balance the brain chemicals serotonin and norepinephrine. This helps increase metabolism, causes a feeling of fullness, and increases energy levels. It may be particularly useful for binge-eaters. Studies indicate that sibutramine is effective in achieving weight loss, although the weight loss slows considerably after the first 3 months. The drug also appears to improve cholesterol and lipid (fat) levels, and may have other effects that benefit the heart.

Side effects of sibutramine are common. They include dry mouth, constipation, and insomnia. In one study, almost half the patients dropped out as a result of these side effects. There have been reports of increases in heart rate and blood pressure while taking this medication, although a 2001 study indicates that blood pressure stabilizes over time.

At this time, people who have a history of high blood pressure, stroke, heart disease, or arrhythmias should not take this drug. People taking decongestants, bronchodilators (such as for asthma), monoamine oxidase inhibitors, or serotonin reuptake inhibitors should also avoid sibutramine.

Phentermine and Other Sympathomimetics. Sympathomimetics are drugs that act like the stress hormone (and chemical messenger) norepinephrine. These medications act as stimulants in the brain. Some are approved for treating obesity, but only for short-term use. They include:

• Phentermine (Ionamin, Adipex-P, Fastin)
• Benzphetamine (Didrex)
• Phendimetrazine (Adipost, Bontril, Melfiat, Plegine, Prelu-2, Statobex)

Phentermine is the most commonly prescribed appetite suppressant, and is less expensive than orlistat or sibutramine. Its effects are not long lasting, however. It can also raise blood pressure. In addition, phentermine is associated with depression, which is already a problem in many cases of obesity. A combination (Phen-Pro) containing phentermine and the antidepressant fluoxetine (Prozac) is being investigated to help reduce this problem. Note: Neither phentermine nor such combinations are associated with the heart problems linked to the previous phentermine combination known as Fen-Phen (phentermine and fenfluramine).

Amphetamines. The amphetamines dextroamphetamine (Dexedrine), methamphetamine (Desoxyn), and phenmetrazine (Pleudin) are powerful stimulants. They were used most often in the past but are no longer prescribed for weight loss. These drugs improve mood and produce some modest weight loss over the short term, but carry serious risks of addiction, agitation, and insomnia.

Rimonabant. Rimonabant (Accompli) belongs to a new class of drugs called selective CB1 blockers. The drug is designed to block receptors in the brain associated with the regulation of eating. Rimonabant also targets receptors in fat tissue. The Rimonabant in Obesity-Lipids (RIO-Lipids) study looked at how rimonabant affected metabolic risk factors in high-risk overweight or obese patients with blood fat disorders. The study involved more than 1,000 participants. The findings, published in the November 2005 New England Journal of Medicine, said that people who took the drug significantly reduced their body weight and size of their waist.

Earlier studies involving the drug reported that obese patients treated with 20 mg of rimonabant lost significantly more weight and inches from their waist than patients who received placebo. The drug also appeared to have beneficial effects on raising HDL ("good") cholesterol levels.

Note: Fake rimonabant has been found for sale on several web sites. Patients should be aware that this drug is still experimental, and rimonabant is not available for sale. Buying and taking counterfeit drugs can have serious health consequences. In addition, an FDA advisory panel in April 2007 rejected the drug, citing fears it may cause psychiatric problems and seizures in some patients.

Axokine. Axokine is a type of drug called a ciliary neurotrophic factor. It signals the brain to suppress one's appetite. It is proving to be effective in achieving weight loss, and also improves cholesterol, lipid, and glucose levels regardless of food intake. It could be particularly helpful for people with type 2 diabetes. Early study results found that severely obese patient who took the drug lost more weight than those who took a dummy pill (placebo). Nearly half (46%) of patients who took the drug lost at least 10 pounds, compared to 5% of those who received the placebo. Study participants tolerated the drug well. There were no reports of serious side effects.

Zonisamide. Zonisamide (Zonegran) is an anti-seizure medication that is also being investigated for weight loss. In one study, patients who took it lost more weight than those on placebo. Zonisamide increases the risk for kidney stones, which can be reduced with increased fluid intake and citrate. It has also been associated with reduced sweating and a sudden rise in body temperature, especially in hot weather. Other side effects include dizziness, forgetfulness, headache, and nausea.

Topiramate. Topiramate (Topamax) is another anti-seizure medication being investigated for weight reduction. Three clinical trials have reported that patients given topiramate lost more weight than those receiving placebo. Weight loss was sustained for up to 1 year. The drug is also being studied for binge-eating disorders associated with obesity.

Other Treatments

Surgical procedures for obesity may be appropriate for some dangerously obese people, and may reduce heart problems and many of the risks associated with obesity. These risks include high blood pressure, sleep apnea, and diabetes. In fact, some evidence suggests that surgery may provide much greater control of weight and diabetes than nonsurgical weight-loss methods. Studies are reporting significant reductions in diabetes, and the need for diabetic medications, after surgery. Other medical conditions that often improve after surgery include heartburn, arthritis, and other joint and circulation problems.

Bariatric surgeries produce weight loss through one of two approaches:

• Restrictive Banding Procedures. These procedures restrict the amount of food by closing off parts of the stomach with bands.
• Malabsorptive Bypass Procedures. This approach restricts the amount of food and also reduces absorption by using a bypass of parts of the intestine.

The malabsorptive procedures are more successful in achieving weight loss than the banding approach, but they carry a greater risk for nutritional deficiencies.

Most people who have bariatric surgery lose about two-thirds of excess weight within 2 years. In addition, diseases associated with obesity (such as diabetes, high blood pressure, sleep apnea, joint pain, and incontinence) often improve.

Researchers at the Mayo Clinic looked at records from patients who had the surgery between 1990 and 2003. They found that those who had bariatric surgery reduced their risk of cardiovascular events such as a heart attack much more than those who lost weight without surgery. The findings were published in the September 2005 Mayo Clinic Proceedings.

Other studies have shown that even though most patients maintain significant weight loss, the majority regain about to 10% of their weight. Patients must still develop a healthy life style and be calorie conscious after the operation. Follow-up must be life-long.

Any surgical candidate must have failed consistently in losing weight through less invasive methods. Experts recommend bariatric surgery only for the following:

• Those whose BMI is above 40 (about 100 pounds overweight)
• Those with BMIs of over 35 who have type 2 diabetes or serious obesity-related medical problems
• Those with severe obesity that interfered with employment, normal physical activity (e.g., walking), and important relationship

About a third of people who undergo these procedures achieve normal weight, and 80% experience some weigh loss. They are less successful than the bypass procedures, but carry a lower risk of nutritional deficiencies.

Vertical Banded Gastroplasty. Vertical banded gastroplasty (VBG) was the most common restrictive procedure. It involves creating a hole through both stomach walls and sealing the edges with a staple. This narrows the stomach, similar to a funnel, and allows only small amounts of food to pass through.

Laparoscopic Gastric Banding. Laparoscopic gastric banding (the Lap-Band) usually does not require a major incision and avoids some of the major complications of gastric bypass:

• It employs an adjustable silicone band that is placed around the upper part of the stomach.
• A small balloon-like reservoir attached to the band under the abdominal skin contains saline, which can be added or removed to tighten or loosen the band.
• The procedure restricts the amount of food a person can eat and gives the feeling of fullness.

The band is removable, if necessary. Studies to date indicate that the intestinal tract returns to normal afterward. Studies, including those done in the elderly, have reported significant weight loss and improved quality of life with the procedure.

Malabsorptive procedures produce greater weight loss than restrictive procedures. Patients generally achieve about two-thirds of their weight loss within 2 years. Furthermore, in a 2003 study, after standard bypass surgery, 83% of patients with type 2 diabetes experienced normal blood glucose levels and the rest had significant reductions.

Roux-en-Y Gastric Bypass Procedure. This is the most common and successful malabsorptive surgery in the United States. It involves creating a small stomach pouch that serves as a reservoir and restricts food intake. The pouch eventually holds up to 3 ounces of food and has a small outlet that delays emptying and causes a feeling of fullness. Then the surgeon creates a Y-shaped section in the small intestine that attaches to the pouch. This section allows food to bypass the lower stomach and upper part of the intestine. One 2003 study reported that this procedure was associated with significant weight loss, and 80% of patients with type 2 diabetes were able to reduce their medications. A more recent study, published in the March 14, 2006, issue of Archives of Surgery, found that gastric bypass surgery also helps lower the blood pressure of very obese patients.

The procedure produces greater and more sustained weight loss than banding procedures, but it is also more complicated, and carries a higher risk of nutritional deficiencies. Laparoscopy techniques, which are less invasive, are now preferred over open surgery. They achieve equally good results with fewer complications.

Biliopancreatic Diversion. This procedure is more complicated and removes portions of the stomach. The pouch that is created attaches directly to the lower part of the small intestine. It poses a higher risk for nutritional deficiencies than other procedures and is not used as often.

Click the icon to see an image of gastric bypass surgery.

General Side Effects and Complications. Side effects and complications of bariatric procedures are common, and up to 25% of patients require corrective or repeat procedures. After any of these procedures people must chew all their food carefully, and they cannot eat large amounts of food at one time. If patients do not follow these guidelines, they will experience nausea, abdominal distress, or both.

Complications from any bariatric procedure includes the following:

• Vomiting: This is the most common complication, and it is most common with banding procedures.
• Nutritional deficiencies: There is a strong risk of nutritional deficiencies, particularly with malabsorptive operations. This complication can lead to anemia and increase the risk of bone loss and osteoporosis. Taking enough mineral and vitamin supplements is important after bariatric surgery.
• Deep-vein thrombosis: There is a significant risk for deep-vein thrombosis (blood clots in the veins).
• Abdominal hernia: This is another common complication. Newer, laparoscopic techniques do not carry this risk, but not all individuals are candidates for this less-invasive approach.
• Rapid weight loss after surgery: This complication puts people at high risk for gallstones.
• Women who wish to be pregnant should wait until their weight has stabilized. Rapid weight loss and nutritional deficiencies can harm the fetus.

People at highest risk for complications are those with heart or lung problems, severe obesity, and a history of abdominal surgeries. The mortality rate from bariatric surgeries is 0.2%, which is lower than the morality rates from severe obesity itself. Other surgical variations and less invasive techniques using laparoscopy have been developed.

Specific Complications of Restrictive Banding Procedures. Nausea, vomiting, or both occurs in half the patients, and severe heartburn occurs in a third. Device-related complications include band slippage, pouch dilation (widening), or both in nearly a quarter of patients, and obstruction in 12% of patients. Very serious complications are rare, but include blood clots, bleeding, infection, pneumonia, and perforation (tearing) of the stomach.

Specific Complications of Malabsorptive Bypass Procedures. Vomiting often occurs. Nutritional deficiencies occur more often in these procedures. The so-called dumping syndrome is a common unpleasant side effect, which occurs when food waste moves too quickly through the intestine. Symptoms include nausea, weakness, sweating, and faintness (particularly after eating sweets).

Liposuction is not recommended for major weight loss.

Resources

• www.healthierus.gov/dietaryguidelines -- Dietary Guidelines for Americans 2005
• www.naaso.org -- North American Association for the Study of Obesity
• www.eatright.org -- American Dietetic Association
• www.nutrition.gov. -- Nutrition.gov
• www.asbs.org -- American Society for Bariatric Surgery
• www.cnpp.usda.gov -- Center for Nutrition Policy and Promotion
• http://fnic.nal.usda.gov -- Food and Nutrition Information Center
• www.americanheart.org -- American Heart Association
• www.nationaleatingdisorders.org -- National Eating Disorders Organization
• www.aabt.org -- Association for Advancement of Behavior Therapy
• www.fda.gov -- Food and Drug Administration
• http://win.niddk.nih.gov -- Weight-Control Information Network

References

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National Center for Health Statistics. Chartbook on Trends in the Health of Americans. Health, United States, 2005. Hyattsville, MD: Public Health Service. 2005

National Institute of Diabetes and Digestive and Kidney Diseases - Weight-control Information Network. Statistics Related to Overweight and Obesity. Available online.

National Center for Health Statistics. Prevalence of Overweight Among Children and Adolescents: United States, 2003-2004.

Morino M, Toppino M, Bonnet G, Rosa R, et al. Laparoscopic vertical banded gastroplasty for morbid obesity. Assessment of efficacy. Surg Endosc. 2002 Nov;16(11):1566-72.

Brethauer SA, Schauer PR, Chand B. Risks and benefits of bariatric surgery: Current evidence. Cleveland Clinic Journal Of Medicine. 2006 Nov; 73(11): 993-1007.

Rosenthal RJ, Szomstein S, Kennedy CI, et al. Laparoscopic surgery for morbid obesity: 1,001 consecutive bariatric operations performed at The Bariatric Institute, Cleveland Clinic Florida. Obes Surg. 2006 Feb;16(2):119-24.

He K, Liu K, Daviglus ML, et al. Magnesium Intake and Incidence of Metabolic Syndrome Among Young Adults. Circulation. 2006: Published online before print. March 27, 2006.

Chen TY, Smith W, Rosenstock JL, Lessnau KD. A life-threatening complication of Atkins diet. Lancet. 2006 Mar 18;367(9514):958.

Lopez-Jimenez F, Bhatia S, Collazo-Clavell ML, Sarr MG, Somers VK. Safety and efficacy of bariatric surgery in patients with coronary artery disease. Mayo Clin Proc. 2005 Sep;80(9):1157-62.

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Fernstrom JD, Courcoulas AP, Houck PR, Fernstrom MH. Long-term changes in blood pressure in extremely obese patients who have undergone bariatric surgery. Arch Surg. 2006 Mar;141(3):276-83.

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Lanningham-Foster L, Nysse LJ, Levine JA. Labor saved, calories lost: the energetic impact of domestic labor-saving devices. Obes Res. 2003 Oct;11(10):1178-81.

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