also called CORPULENCE, or FATNESS, excessive accumulation of body fat, usually caused by the consumption of more calories than the body can use. The excess calories are then stored as fat, or adipose tissue. Overweight, if moderate, is not necessarily obesity, particularly in muscular or large-boned individuals. In general, however, a body weight20 percent or more over the optimum tends to be associated with obesity.

The body's ability to adjust food intake to body needs can be disturbed by numerous factors. Of these, hormone imbalances and glandular defects are believed to be of least importance, being demonstrable in only bout 5 percent of all obese individuals. Although obesity may be familial, suggestive of a genetic predisposition to fat accumulation, there is also evidence that early feeding patterns imposed by the obese mother upon her offspring may play a major role in a cultural, rather than genetic, transmission of obesity from one generation to the next. More generally, the distinctive way of life of a nation and the individual's behavioral and emotional reaction to it may contribute significantly to widespread obesity. Among the affluent populations, an abundant supply of readily available high-calorie foods and beverages, coupled with increasingly sedentary living habits that markedly reduce caloric needs, can easily lead to overeating. The stresses and tensions of modern liv!ing also cause some individuals to turn to foods and alcoholic drinks for "relief."

Obesity may be undesirable from an aesthetic sense, especially in parts of the world where slimness is the popular preference; it is also a serious medical problem. Generally, obese persons have a shorter life expectancy; they suffer earlier, more often, and more severely from a large number of diseases than do their normal-weight counterparts. They are also more likely to die prematurely of degenerative diseases of the heart, arteries, and kidneys. More die of accidents and diabetes, andmore constitute poor surgical risks than persons with normal weight. Mental health is also affected; behavioral consequences of an obese appearance, ranging from shyness and withdrawal to overly bold elf-assertion, may be rooted in neuroses and psychoses.

The treatment of obesity has two main objectives: removal of the causative factors, which may be difficult if the causes are ofemotional or psychological origin; and removal of surplus fat by reducing food intake. Return to normal body weight by reducing calorie intake is best done under medical supervision. Dietary fads and reducing diets that produce quick results without effort are of doubtful effectiveness in reducing body weight and keeping it down, and most are actually deleterious to health. (See dieting.)

Obesity is to be distinguished from overweight caused by edema (excess retention of fluids) stemming from various diseases.