Effects of Weight Loss
on Morbidity and Mortality
EDWARD W. GREGG
DAVID F. WILLIAMSON
The concept that, for a given height, there is a range of low-morbidity or low-mortality body weights, is firmly established in epidemiology (see Chapter 76). There is less agreement, however, over the spread of such ranges. Weights within these ranges have been called ideal, desirable, optimal, healthy, or recommended body weights. This general concept has two important implications that constitute the basis of modern weight management guidelines: First, people with body weights outside the recommended range, particularly the overweight, are at risk for chronic disease and even premature death; second, overweight people can lower their health risks by losing weight. Current epidemiological evidence generally supports the first inference but is equivocal about the second. Studies of weight loss are more susceptible than are studies of weight itself to confounder bias, such as underlying illness. Given the high prevalence of overweight and obesity, elucidating the effects of weight loss on health is a priority.
Table 88.1 demonstrates the widespread desire to lose weight in the U.S. population. About 29% and 43% of adult men and women, respectively, report trying to lose weight. In all body mass index (BMI) categories, women want to lose more weight than men except in the underweight category, where both men and women want to gain weight, but women want to gain much less weight than men (1.2 vs. 5.4 kg). Overall, women want to lose 7.9 kg and men, 4.2 kg.