Being overweight appears associated with slightly lower all-cause mortality

A systematic review published in the January 2013 issue of JAMA found that being classified as "overweight” on the BMI scale was associated with significantly lower all-cause mortality, although "obesity” was associated with significantly higher all-cause mortality, when compared to normal weight. More specifically, the study found grade 1 obesity was not associated with higher all-cause mortality, and grades 2 and 3 obesity were associated with significantly higher all-cause mortality.

The researchers noted the study’s limitations, such as addressing only all-cause mortality and not morbidity, and the limitations of using the BMI scale versus other methodologies to measure body composition. These and other limitations of the controversial study are further expanded upon in a review by David L. Katz, MD, MPH, FACPM, who notes that individuals are living longer—but sicker—and that this study does not undo what we know about weight management and health.