Changes in commingled body mass index distributions associated with secular trends in overweight among Danish young men.

The authors present results from a novel approach to understanding recent secular trends in overweight in terms of changes in underlying component distributions. On the basis of an examination of two large overlapping samples of Danish young men (ns = 16,557 and 21,747) spanning birth cohorts 1939-1958, the authors found evidence for two-component distributions, normal and overweight, in all cohorts. In cohorts born after 1940, the authors observed an increase in the size of the overweight component with no corresponding changes in overall mean or component means. On the basis of these results and other published reports, the authors speculate that the secular increase in overweight may be understood as a differential response to environmental change that may be mediated by genotype. The net effect appears to have been an increased penetrance in obesity-prone Danish young men.