Lifetime weight patterns in male physicians: the effects of cohort and selective survival

The natural history of lifetime weight change is not well understood because of conflicting evidence from cross-sectional and longitudinal studies. Cross-sectional analyses find that adult weight is highest at approximately 60 years of age and lower thereafter. Longitudinal analyses have not found this pattern. Our objective was to test whether cohort effects and selective survival may explain the differences observed between cross-sectional and longitudinal studies.

We analyzed data on white men from the Johns Hopkins Precursors Study (n = 1197). Weight and height were measured at enrollment during medical school. The Precursors Study collected subsequent weight measurements by self-report and follows all participants for mortality.

In preliminary analyses that ignored cohort and survival effects, average weight increased 0.16 kg/yr to age 65 (p < 0.001) and declined 0.10 kg/yr thereafter (p = 0.002). When controlling for differing rates of weight change by cohort and survival group, the apparent decline after 65 years of age was mostly explained.

These data suggest that, in white men, weight increases steadily until age 65 and then plateaus. These findings emphasize the necessity of longitudinal rather than cross-sectional data to describe lifetime weight patterns.