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Abstract: We estimate trends in BMI values by deciles of the US adult population by birth cohorts 1882–1986 stratified by ethnicity and gender. The highest decile increased by some 18–22 BMI units in the course of the century while the lowest ones increased by merely 1–3 BMI units. For example, a typical African American woman in the 10th percentile and 64in. (162.6cm) tall increased in weight by just 12 pounds (5kg) whereas in the 90th percentile her weight would have increased by 128 pounds (58kg). Hence, the BMI distribution became increasingly right skewed as the distance between the deciles increased considerably. The rate of change of the BMI decile curves varied greatly over time and across gender and ethnicity. The BMI deciles of white men and women experienced upswings after the two world wars and downswings during the Great Depression and also decelerated after 1970. However, among African Americans the pattern is different during the first half of the century with men''s rate of increase in BMI values decreasing substantially and that of females remaining constant at a relatively high level until the Second World War. After the war, though, the rate of change of BMI values of blacks came to resemble that of whites with an accelerating phase followed by a slowdown around the 1970s. [Copyright &y& Elsevier]

Background: The trend in the body mass index (BMI) values of the US population has not been estimated accurately because the time series data are unavailable and the focus has been on calculating period effects., Objectives: To estimate the trend and rate of change of BMI values by birth cohorts stratified by gender and ethnicity born 1882-1986., Methods: We use loess additive regression models to estimate age and trend effects of BMI values of US-born black and white adults measured between 1959 and 2006. We use all the National Health Examination Survey and National Health and Nutrition Examination Survey data., Results: The increase in BMI was already underway among the birth cohorts of the early 20th century. The rate of increase was fastest among black females; for the three other groups under consideration, the rates of increase were similar. The generally persistent upward trend was punctuated by upsurges, particularly after each of the two world wars. The estimated rate of change of BMI values increased by 71% among black females between the birth cohorts 1955 and those of 1965 is indicative of the rapid increases in their weight., Conclusions: We infer that transition to postindustrial weights was a gradual process and began considerably earlier than hitherto supposed., ((c) 2010 Wiley-Liss, Inc.)