Eating right is only one step in controlling America’s weight epidemic.

More than 50% of adults in the United States are overweight and one in five is obese, according to the Centers for Disease Control and Prevention—approximately 25% of women and 19.5% of men. Over 97 million adults in the United States are obese, according to estimates published by the National Heart, Lung, and Blood Institute in 1998. These adults have a 50–100% increased risk of death from cardiovascular diseases, such as diabetes, heart disease, and stroke. The World Health Organization considers obesity an international epidemic, stating in 1997 that “obesity’s impact is so diverse and extreme that it should now be regarded as one of the greatest neglected public health problems of our time with an impact on health which may well prove to be as great as that of smoking.”

Obesity Defined
The National Institutes of Health (NIH) established distinct standards for what constitutes overweight and obesity in June 1998. According to clinical guidelines, overweight is defined as an excess of body weight that may come from muscle, bone, fat, and/or body water as compared with set standards. This is in contrast to obesity, which is defined as an abnormally high proportion of body fat. Thus, although all obese people are overweight, not all overweight people are obese. For example, some athletes are classified as overweight simply because they have a lot of muscle. Most doctors say that men with more than 25% body fat and women with more than 30% body fat are obese. As a general rule, women have more body fat than men. The body needs fat to function—it’s used for stored energy, heat insulation, and shock absorption.

Researchers and health professionals generally determine obesity using the body mass index (BMI). This is a nongender-specific calculation based on height (in.) and weight (lb) using the equation

According to the NIH, obese people have a BMI of 30 or greater, while the BMI for overweight people is 25 or greater.

Causes: Genes vs. Lifestyle
Weight gain occurs when more calories are consumed than are burned in the form of energy. The exact reason for this disparity is unclear, but evidence suggests that genetic, environmental, and psychological factors contribute to an extreme amount of weight gain that leads to obesity, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Weight-Control Information Network. Obesity can also be the result of some rare diseases, such as hypothyroidism and Cushing’s syndrome, and some antidepressant and steroid medication can cause excessive weight gain. However, experts believe that these causes are only responsible for about 1% of obesity cases.

“There are many different forms of this disease and probably many different causes,” says Arthur Frank, medical director of the George Washington University Weight Management Program (Washington, DC). “The eating regulating system is very complex, and many things can become dysfunctional. It is naïve to blame obesity on ‘poor’ eating. Eating is not merely a matter of choice since so much of it is driven by neurochemistry.”

Obesity often runs in families, and many researchers believe that genetics may account for 40–50% of obesity, adds Frank, because an individual inherits a particular biochemical or neurochemical metabolism. Some people inherit a stable food regulating system that enables them to maintain a healthy body weight; others inherit an unstable or fragile food regulating system. “The way we eat is profoundly affected by the regulating system,” says Frank. “We can choose to modify our eating, but it is very difficult to do that. This is why it’s such a difficult disease to manage.”

A recent study at Beth Israel Deaconess Medical Center in Boston also found that a single enzyme in fat cells (11 beta HSD-1) might be to blame for visceral obesity—a large amount of fat concentrated in the abdomen—commonly known as a “beer belly”. This enzyme produces cortisol, the fight-or-flight hormone that helps people survive in stressful situations. But it also produces cortisol in cells not normally associated with the hormone. An elevated level of cortisol is linked to visceral weight gain. Thus, an increase in this enzyme can lead to an increase in cortisol production, which leads to obesity and obesity-related diseases.

Some of the environmental factors that influence obesity include attitudes toward diet and exercise. If parents eat mainly high-fat foods and are sedentary, their children will most likely imitate their behavior. This conclusion is countered, however, by a study that found that adults who were adopted as children were more similar in weight to their biological than to their adoptive parents. Results of the study indicated that genetics had more influence over an individual’s weight than the environment provided by the adoptive parents.

Health Consequences
Most cases of diabetes are due to overweight and obesity, according to a recent study by the American Diabetes Association. In the United States, diet-related illnesses cost more than $80 billion a year in medical expenses, and overweight is the leading risk factor for cardiovascular disease. Health risks associated with obesity include high cholesterol, diabetes, heart disease, stroke, hypertension, gallbladder disease, and some forms of cancer, including those of the breast and uterus.

Obesity is also linked to emotional trauma. American society considers physical attractiveness and slim proportions to be of paramount importance. Thus, many people who fall outside these boundaries are seen as slothful and lazy and face stigmatization at many levels: at school, at work, and in social settings. Feelings of shame and rejection follow, which in turn can lead to severe depression. Addressing the psychological effects of obesity, Frank says, “There is no brief answer except to say that it is devastating. It shatters the lives of patients.”

Treatments
The American Obesity Association (AOA) outlines the following treatment options for obesity: lower calorie diets, increased physical activity, lifestyle changes, drug therapies to boost weight loss, and surgery. None of these options are mutually exclusive. Necessary life style changes include a strict diet regimen and daily exercise. But for many obese individuals, this is not enough to decrease weight fast enough to address immediate health concerns; therefore, medication becomes a part of the treatment regimen. For people who are severely obese (BMI of 40 or more), surgery is an option.

Drugs. Most obesity prescriptions take the form of appetite suppressants, which decrease the appetite by increasing the level of the chemicals in the brain that regulate eating, such as catecholamine, serotonin, dopamine, or norepinephrine.

Weight loss varies among people taking appetite suppressants; some patients can lose more than 10% of their starting body weight, an amount that greatly reduces risk factors for heart disease and diabetes. But most people reach the maximum amount of weight loss within the first six months on medication, after which their weight reaches a plateau or may even increase. In addition, the brain starts to compensate and develop ways of overcoming the appetite suppression, usually within the first three or four months on the medication.

Controversy surrounds appetite-suppressant medications, especially after the U.S. Food and Drug Administration (FDA) banned fenfluramine, which, with its partner phentermine, formed the infamous drug combination fen–phen. This popular diet regime was shown to cause heart valve damage, prompting the FDA to issue a ban in 1997. The agency did not ban phentermine, and, according to Frank, it is still the biggest selling obesity drug in the United States.

The FDA has approved most of the appetite suppressants currently on the market for short-term use—from a few weeks to a year. Sibutramine (Meridia) is the only appetite suppressant ap proved for longer use, although its safety and effectiveness beyond one year have not been determined. According to a paper published in The Lancet in December 2000, sibutramine can help maintain weight loss in conjunction with a reduced-calorie diet for up to two years. But even in the short term, the resulting weight loss can reduce a number of health risks by lowering blood pressure and decreasing insulin resistance, which inhibits the body’s ability to process sugar.

Another obesity drug currently on the market is not an appetite-suppressant, but a lipase inhibitor. Orlistat (Xenical) was approved by the FDA in April 1999 and works by blocking absorption of fat by attaching itself to the enzyme that allows fat to pass across the intestinal wall. Reported to block up to 30% of fat absorption, orlistat still allows proteins and carbohydrates to be absorbed into the body.

Surgery. If these treatment options—drug therapy, diet modification, exercise—have been tried, and the individual is still severely obese, many doctors recommend surgery, which changes the way the body digests and absorbs food, leading to weight loss.

There are two types of obesity surgery: food intake restriction and malabsorption. Food intake restriction involves closure or removal of part of the stomach using bands or staples placed near the top of the stomach. Once the stomach becomes smaller, the appetite decreases because the amount of food it can hold decreases. Malabsorption involves the small intestine, where most of food digestion and absorption occurs. This surgery removes part of the small intestine or changes where it connects to the stomach. Like food intake restriction, this limits the amount of food that is digested and absorbed.

Surgery, drug therapy, and diet are all important factors in the treatment of obesity, but Frank believes future understanding of the disease lies in studying the neurochemistry and endocrinology behind the eating regulation system. In fact, Frank believes that surgery will ultimately be abandoned once other interventions improve. “Appetite is a complicated system with many different parts,” says Frank. “Medications affect one part of the system for a period of time, but then the brain starts to compensate and develop ways of overcoming the appetite suppression. In order to understand obesity, we must take apart the whole system, try to figure out ways to affect the system, and then look at how to avoid this compensation.”