Obesity

obesity, condition resulting from excessive storage of fat in the body. Obesity has been defined as a weight more than 20% above what is considered normal according to standard age, height, and weight tables, or by a complex formula known as the body mass index. It has been estimated that 30% to 35% of Americans are overweight or obese.

Health and Social Implications

Obesity is a major public health concern because it predisposes the individual to many disorders, such as noninsulin-dependent diabetes, hypertension, stroke, and coronary artery disease, and has been associated with an increased incidence of certain cancers, notably cancers of the colon, rectum, prostate, breast, uterus, and cervix. In contemporary American society, obesity also carries with it a sometimes devastating social stigma. Obese people are often ostracized, and discrimination against them, especially in hiring and promotion, is common.

Causes of Obesity

Obesity research has yielded a complicated picture of the underlying causes of the condition. The simple cause is ingestion of more calories than are required for energy, the excess being stored in the body as fat. Inactivity and insufficient exercise can be contributing factors; the less active the person, the fewer calories are needed to maintain normal body weight. Overeating may result from unhealthful patterns of eating established by the family and cultural environment, perhaps exacerbated by psychological distress, an emotional dependence on food, or the omnipresence of high-calorie foods.

In some cases, obesity can come from an eating disorder. It has been shown, for example, that binging for some people releases natural opiates in the brain, providing a sense of well-being and physical pleasure. Other studies have found a strong relationship between obesity in women and childhood sexual abuse.

Some weight-loss experts see obesity as based upon genetics and physiology rather than as a behavioral or psychological problem. For example, rat studies have shown that fat cells secrete a hormone that helps the rat's brain assess the amount of body fat present. The brain tries to keep the amount of that hormone (which also appears to act on the brain area that regulates appetite and metabolic rate) at a set level, resulting in the so-called set point—a weight that the body comes back to, even after resolute dieting. The gene that encodes this hormone, called the obese or ob gene, has been isolated in both rats and humans. In addition, a gene that influences obesity and the onset of diabetes has been identified. It has been estimated that from 8 to 30 different genes may influence obesity.

Treatment

Radical treatments for weight loss have included wiring shut the jaw, stapling the stomach, and intestinal bypass operations circumventing a large area of the small intestine, limiting the area where food is absorbed. The "diet pills" of the 1960s, essentially amphetamines such as Dexedrine, are now seldom prescribed for weight loss. Fenfluramine and dexfenfluramine, drugs formerly used to achieve short-term weight loss, were withdrawn from the market following concerns that they could cause heart valve damage. Drugs available by the late 1990s included sibutramine (Meridia), which is an appetite suppressant, and orlistat (Xenical), which acts to block absorption of dietary fat in the intestine. In 2007 an over-the-counter version of orlistat was approved by the Food and Drug Administration.

Although the study of obesity is yielding many possibilities for treatment, the main focus remains diet (especially a diet limiting fat calories) and exercise, often coupled with emotional and behavioral support. The long-term weight-loss success of most attempts at dieting, however, is notoriously low. Groups such as Overeaters Anonymous, modeled after Alcoholics Anonymous, give support to people with weight problems and eating disorders.

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obesity

Excessive body fat. It is usually caused by sedentary habits and a diet high in fat, alcohol, or total calories. Calories consumed but not used are stored as fat. Rare causes include glandular defects and excess steroids (see Cushing syndrome). Obesity raises the risk of heart disease and diabetes mellitus. Treatment, by reducing calorie intake and increasing exercise, is best undertaken with a doctor's advice.

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obesity [ō′bē·səd·ē]

(medicine)

An excessive accumulation of body fat which confers health risks such as diabetes, cardiovascular diseases, arthritis, and some types of tumors.

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Obesity 

the excess accumulation of fatty tissue in man that results from overeating combined with insufficient muscular activity. Obesity is a disease that results from the predominance of fat synthesis and storage over fat breakdown.

One of the principal mechanisms responsible for obesity is the disruption of the coordination between fat metabolism and carbohydrate metabolism. This disruption intensifies the conversion of carbohydrates to fats. A pathological metabolism or tendency toward abnormally large fat cells can be hereditarily transmitted. Overeating in general and the overconsumption of carbohydrate foods, such as dishes that contain flour and sugar, encourage the manifestation of a hereditary predisposition to obesity.

Obesity can also result from certain diseases of the central nervous system or from endocrine disorders—especially a failure in hypothalamic regulation. Metabolic disturbances, poor eating habits, and lack of exercise can also lead to obesity. Although the disease can occur at any age, it usually first appears in childhood. The greatly increased incidence of obesity in the 20th century is also related to scientific and technological progress, for example, automation and mechanization of many industrial and household processes with the corresponding decrease in muscular activity. According to the World Health Organization (1972), about 30 percent of the population of the economically developed countries is 20 percent or more over the normal weight. The average life expectancy of obese individuals is five to ten years below normal.

Obesity is manifested by a considerable increase in weight, owing to the accumulation of fat in the subcutaneous fatty tissue, omentum, mediastinum, pericardium, and renal capsule. It interferes with the functioning of the heart, alters the locomotor apparatus, and promotes early aging. Metabolic disturbances that result from obesity can lead to the development of atherosclerosis and diabetes mellitus. Several degrees of obesity are distinguished: first-degree obesity involves a 29-percent weight increase above normal; second-degree, a 30- to 49-percent increase; third-degree, a 50- to 99-percent increase; and fourth-degree, a 100-percent or greater increase. Fat is sometimes deposited evenly, sometimes only in one part of the body; the latter, localized, form of obesity is called lipomatosis.

Obesity is treated with a properly balanced diet, a supervised health regimen, dietotherapy, physical therapy, and anorexigenics. In complicated forms of obesity, efforts are made to eliminate the underlying causes. Prevention of obesity must start in childhood with the establishment of such routines as a properly balanced diet and a healthy amount of physical activity.

REFERENCES

Leites, S. M. Patofiziologiia zhirovogo obmena. Moscow, 1964. (Bibliography.)
Egorov, M. N. “Ozhirenie.” In Mnogotomnoe rukovodstvopo vnutrennim bolezniam, vol. 8. Edited by E. M. Tareev. Moscow, 1965.
Leites, S. M., and N. N. Lapteva. Ocherkipo patofiziologii obmena veshchestv i endokrinnoi sistemy. Moscow, 1967.
Prediabet i ozhirenie. Moscow, 1973.

IU. A. KNIAZEV