3 minute read


A condition of having an excessive accumulation of fat in the body, resulting in a body weight that is at least 20 percent above normal when measured against standard tables of optimal weight ranges according to age, sex, height, and body type.

Individuals who are 20 percent overweight are considered slightly obese. Those who are 40 percent above standard weight are moderately obese, while those 50 percent above it are morbidly obese. Persons who exceed desired weight levels by 100 pounds (45 kg) or more are hyperobese. Obesity is a serious health problem in the United States. Studies suggests that between 10 and 20 percent of Americans are slightly to moderately obese. Obesity places stress on the body's organs, and is associated with joint problems, high blood pressure, indigestion, dizzy spells, rashes, menstrual disorders, and premature aging. Generally, when compared to persons of normal weight, obese individuals suffer more severely from many diseases, including degenerative diseases of the heart and arteries, and a shorter life expectancy. Obesity can also cause complications during childbirth and surgery.

Obesity may be familial, as the body weight of children appears to be linked to that of their parents. Children of obese parents have been found to be 13 times more likely than other children to be obese, suggesting a genetic predisposition to body fat accumulation. Recent animal research suggests the existence of a "fat gene," and the tendency toward a body type with an unusually high number of fat cells—termed endomorphic— appears to be inherited. However, the generational transmission of obesity may be as cultural as it is genetic, as early feeding patterns may produce unhealthy eating habits.

Some cases of obesity have a purely physiological cause, such as glandular malfunction or a disorder of the hypothalamus. Individuals with a low production of the hormone thyroxin tend to metabolize food slowly, which results in excess unburned calories. When more calories are consumed than the body can metabolize, excess calories are stored in the body as fat, or adipose tissue. Some persons with hypoglycemia have a specific metabolic problem with carbohydrates that can also lead to the storage of unburned calories as fat.

In the great majority of cases, however, obesity is caused by overeating. Overeating itself often combines physical and psychological components. People may eat compulsively to overcome fear or social maladjustment, express defiance, or avoid intimate relationships. However, researchers have also suggested physical correlates for overeating, including deficits in the neurotransmitter serotonin that increase cravings for carbohydrates, and possibly a higher "set point" for body weight that makes obese persons feel hungry more often than thinner people. This raised set point could result from both genetics and early nutritional habits. Lack of exercise and sedentary living also contribute to obesity.

The most effective treatment of obesity includes both the reduction of surplus body fat and the elimination of causative factors, and is best accomplished under medical supervision. An appropriate weight loss plan includes exercise (which burns calories without slowing metabolism), reduced food intake, behavior modification to change food-related attitudes and behavior, and psychotherapy if there are underlying psychological causes for overeating. Other possible treatment measures include hormone therapy, appetite-suppressant drugs, and surgical intervention to alter satiety signals by reducing the size of the stomach and intestines.

Behavior modification has been especially successful and widely used in the treatment of obesity. Treatment techniques include stimulus control (removing environmental cues that play a role in inappropriate eating), eating management (slowing the pace of eating to allow satiation to catch up with it), contingency management (applying a system of positive reinforcement and punishments), and self-monitoring of daily dietary intake and factors associated with it. Despite all of the available treatments, the difficulty of reversing obesity in adults makes

Source: Centers for Disease Control, U.S. Department of Health and Human Services.


Prevalence of overweight Doubled since 1965
Number who are overweight 4.7 million
Percent who are overweight 11 percent
Related disorders Elevated blood cholesterol; high blood pressure; increased adult mortality
Social consequences Excluded from peer groups, discriminated against by adults, experience psychological stress, poor body image, and low self-esteem.

preventative treatment an important factor during childhood. Today, an increasing percentage of children in the United States are overweight. Recent studies have shown that metabolic rates of children are lower when they watch television than when they are at rest. Unhealthy eating patterns and behaviors associated with obesity can be addressed by programs in nutrition, exercise, and stress management involving both children and families.

Additional topics

Psychology EncyclopediaPsychological Dictionary: Ibn Bajjah (Abu-Bakr Muhammad ibn-Yahya ibn-al-Saʼigh, c.1106–38) Biography to Perception: cultural differences