Overweight Adults May Have the Lowest Mortality. Do They Have the Best Health?

Anna Zajacova, University of Wyoming

Several recent studies have reported that overweight adults experience lower mortality than those who are underweight, normal-weight, or obese. These widely-publicized findings carry critical implications for public health policy because they suggest that overweight may be the optimal weight category for adult health and longevity. In this study, we test this assumption using nationally representative NHANES surveys (2005-2008) with adults age 20-80 (N=9,655). We employ generalized additive models, a type of semiparametric model, to examine the relationship between body mass and key biological risk measures, including inflammatory markers and indicators of respiratory, cardiovascular, and metabolic function. The key finding is that the association between BMI and biological risk factors is generally monotonically increasing rather than U-shaped as mortality analyses suggest. We document the modifying effects of age on the BMI-risk association and attempt to reconcile our findings with those from the mortality literature.