BACKGROUND: During the past 40 y, there has been a trend toward more eating away from home, increased food availability, the opportunity to order extra-large portion sizes, and general weight gain. OBJECTIVE: Because shorter people need fewer calories than taller people to maintain their weight, our goal was to determine whether the body mass index (BMI)-height relation has changed over time. DESIGN: Data are from 3581 nonpregnant women and 3091 men examined in the 1959-1962 National Health Examination Survey and 4651 nonpregnant women and 4691 men examined in the 2001-2004 National Health and Nutrition Examination Survey. We tested whether the relation between BMI and height has changed for men and women, after adjustment for other demographic changes. RESULTS: In the past, on average, shorter American men and women had significantly higher BMIs than taller people. However, taller people have been increasing their BMI during the past 40 y at a faster rate than shorter people. CONCLUSIONS: This study documents that the obesity epidemic has changed the height-BMI relation. The data cannot identify causal pathways, and there are numerous explanations. A plausible hypothesis is that changes in the food environment may have eliminated constraints on weight gain for taller people that existed in a more calorie-constrained environment.
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