OBESITY IS A condition of excess fatness that results from an imbalance between energy consumed and energy expended. In other words, when the human body takes in more food than it uses up, the extra is stored in fat deposits, resulting in increased weight. But obesity is a relative term. Any definition of obesity is arbitrary and subject to shifts in perceptions, both on the part of health experts and the general public. Dr. F. Xavier Pi-Sunyer, one of the country's leading experts on obesity, points out that determining whether someone is obese depends on a number of factors:

A population cannot be precisely divided into normal and obese... . In the modern world, with the great intermixing of ethnic and racial groups, wide genetic heterogeneity exists. The heterogeneity is manifested by differing heights, body circumference (chest, waist, hips...