Albert J. Stunkard
OBESITY is a condition characterized by excessive accumulations of fat in the body. By convention, obesity is said to be present when body weight exceeds by 20 percent the standard weight listed in the usual height-weight tables. 9 This index of obesity, however, is only an approximate one at lesser degrees of overweight, since bone and muscle can make a substantial contribution to overweight. In the future, diagnosis will probably be based upon newer and more accurate methods of estimating. Skin-fold calipers have already gained acceptance because of their convenience and because half of body fat is localized in subcutaneous tissue. 61 But for most clinical purposes the eyeball test is still the most reasonable: If a person looks fat he is fat.
Strikingly little information is available about the prevalence of obesity. Since most good diagnostic methods are too cumbersome for use in large-scale studies, much of our information is derived from height and weight data of poor quality, averaged over populations, and subjected to the criterion of 20 percent over standard weight. Present data suggest that prevalence of obesity reaches a peak at age forty when 35 percent of men and 40 percent of women can be designated as obese.9,80
There have been studies of more limited populations utilizing more reliable data that permit more valid inferences. Unfortunately, these studies differ in their criteria of obesity, making their data difficult or impossible to use for comparisons with other studies. These studies show a striking effect of age, with a monotonic increase in the prevalence of obesity between childhood and age fifty, and a twofold increase between ages twenty and fifty. 53 At age fifty, prevalence falls sharply, presumably because of the very high mortality of the obese from cardiovascular disease in the older age groups. Since these studies use the height-weight criterion, and since the fat content of the body increases per unit weight with age, these studies almost certainly underestimate the