The impact of obesity on US mortality levels: the importance of age and cohort factors in population estimates.

To estimate the percentage of excess death for US Black and White men and women associated with high body mass, we examined the combined effects of age variation in the obesity-mortality relationship and cohort variation in age-specific obesity prevalence. We examined 19 National Health Interview Survey waves linked to individual National Death Index mortality records, 1986-2006, for age and cohort patterns in the population-level association between obesity and US adult mortality. The estimated percentage of adult deaths between 1986 and 2006 associated with overweight and obesity was 5.0% and 15.6% for Black and White men, and 26.8% and 21.7% for Black and White women, respectively. We found a substantially stronger association than previous research between obesity and mortality risk at older ages, and an increasing percentage of mortality attributable to obesity across birth cohorts. Previous research has likely underestimated obesity's impact on US mortality. Methods attentive to cohort variation in obesity prevalence and age variation in obesity's effect on mortality risk suggest that obesity significantly shapes US mortality levels, placing it at the forefront of concern for public health action.