obesity

obesity is most commonly defined as a condition of weighing at least 20% over ideal body weight, where ideal body weight is determined in the US by the 1959 or 1983 Metropolitan Life Insurance Company Tables. Like many aspects of obesity, use of life insurance tables as the sole indicator remains controversial. These insurance charts do not take into account the changes in ideal weight with age or provide information on body fat distribution; nor do they base measurements on all ethnic groups and those of the lower socioeconomic classes. To counter such biases, obesity can be determined by body mass index (which relates weight to height) and the percentage of body fat.

The causes of obesity continue to be debated and studied. Though it has long been considered the simple result of too little exercise and too much eating, new research suggests there may also be some hereditary influence, and particularly that the genetic tendency for obesity may be correlated to the mother's weight. Relatively unusual causes include adult-onset diabetes, deficient thyroid hormone secretion, and, very rarely, tumours of the adrenal gland, pancreas, or pituitary gland. Unexplained abnormal function of the brain's appetite control centre may also play a role. Researchers are particularly concerned about the increasing number of children and adolescents who are overweight in the US and Europe.

Obesity may cause a variety of health complications. Most clearly, overweight has an adverse effect on life expectancy. In general, the greater the degree of overweight, the higher the mortality or excess death rate. Obesity may be associated with elevated blood cholesterol, and has been linked to hypertension, diabetes, cancer, coronary artery heart disease, degenerative arthritis, gall stones, sleep disorders, and depression.

For many the ‘psychological burden’ of being obese in Western cultures, which prize slenderness, particularly in women, is an additional adverse effect. Prior to the nineteenth century, overweight and fatness stood as a sign of health and prosperity, and conveyed social esteem. By the mid and late nineteenth century, a new ethos emerged which championed slenderness as a sign of both beauty and physical health. By the early twentieth century, on the other hand, obesity became associated with laziness, gluttony, and the lower classes. As Keith Walden has written, ‘females who stayed slim demonstrated that they had the money and sense to buy nutritious foods and eat balanced meals, and that they had the time to exercise. They did not have menial jobs which required substantial brawn to perform.’ In twenty-first-century Western culture, especially for whites, and the middle and upper classes, the abhorrence of fat and obesity continues. As Anne Beller describes it, fat is suicidal: a sin at best and at worst a sort of felony. Yet for many African Americans and Hispanics, as well as other ethnic groups, a larger body still holds positive social value.

Suggested treatments for obesity range from a plethora of rarely successful fad diets to medical procedures such as stapling the stomach to reduce intake or shortening the intestines to curtail absorption. The most tried and true method remains adjustment of the energy balance — decreasing caloric intake while increasing energy usage. Vigorous exercise not only ‘burns’ nutrient stores but is also shown in some situations to increase metabolic rate for up to 15 hours after activity. Those with a hereditary tendency toward obesity find it more difficult to lose weight, due to a lower resting metabolic rate and possible complications in appetite regulation. In this regard, and in evolutionary terms, a tendency toward obesity can actually have survival value — a lower metabolic rate and a substantial fat store would allow one to live longer in times of famine. But in the contemporary West, where food is relatively plentiful and slenderness highly prized, it works to one's disadvantage.

Margaret A. Lowe

Bibliography

Beller, A. S. Fat and thin: a natural history of obesity. Farrar, Straus and Giroux, New York.
Walden, K. (1985). The road to Fat City: an interpretation of the development of weight consciousness in Western society. Historical reflections, 12, 331–73.

See also body composition; dieting; energy balance; weight.