Demographics of Obesity
DAVID F. WILLIAMSON
Weight gain in most adults is due to body-fat accumulation. Obesity results when such accumulation becomes excessive and threatens health. Current methods for measuring excess body fat are impractical for large-scale use; therefore, epidemiologists must rely on simple body measurements to detect excess weight in individuals and populations (see Chapter 11). Some weight-by-height indices correlate well with body fat. Epidemiologists routinely use these indices in populations to estimate body weights with the lowest morbidity or mortality and to determine the health risks assumed by individuals who exceed those weights (see Chapter 76). There have been two major approaches to identifying healthy body weights.
First, the Metropolitan Life Insurance Company pioneered this effort with its widely used weight-by-height tables. The 1959 Metropolitan tables were based on data pooled from 26 insurance companies in the United States and Canada. These tables list ranges of body weights for specific heights, with the lowest mortality, extracted from 4.9 million insurance policies issued between 1935 and 1953. The ranges of the height-specific weights are listed by sex and three body frames (small, medium, large) for subjects between 25 and 59 years of age. Cases of heart disease, cancer, or diabetes were excluded. The most recent Metropolitan tables were issued in 1983, using a similar approach (25 companies, 4.2 million insurance policies issued between 1950 and 1971). At comparable heights, the weights with the lowest mortality in the 1983 tables were higher than those in the 1959 tables. The labels “ideal” or “desirable” introduced with these tables for recommended body weights remain popular in the obesity literature (see Chapters 76 and 91). However, despite their continued use and the richness of the data supporting them, the Metropolitan tables lack universal applicability. These tables are based on data from