Analysis in action: public health impact of excess weight

We recently used data from the NPHS to contribute to a heated debate about the public health impact of excess weight. This debate was sparked by an article "Excess Deaths Associated With Underweight, Overweight, and Obesity" by Flegal et al. in the Journal of the American Medical Association. A central question was raised: is being overweight protective against mortality risk?

We used longitudinal, nationally representative data in a partial replication of this study to address several questions. Our analysis confirmed findings in the US analysis: when compared to the body mass index (BMI) category now considered “normal,” being overweight appears to be protective against mortality. However, when this “normal” BMI category is divided further, and the lowest risk category used as reference group, the association between excess weight and mortality changes. In this case, being overweight is no longer protective.

More research, including in-depth analyses of existing longitudinal population-based data sets, is required to adequately understand the association between excess weight and mortality.