Only Substantial Obesity Is Associated with All-Cause Mortality

The reported relation of overweight or obesity to mortality for any given follow-up has been inconsistent, because studies have used varying definitions and categories of normal weight and obesity. In this meta-analysis, researchers identified 97 studies, mostly from the U.S., Europe, and Australia (2.88 million participants and >270,000 deaths), in which weight categories were standardized. Participants were categorized by body-mass index (BMI) as normal weight (18.5 to <25 kg/m²), overweight (25 to <30), grade 1 obese (30 to <35), grade 2 obese (35 to <40) and grade 3 obese (≥40).

Compared with normal-weight participants, all-cause mortality was significantly lower for overweight participants (hazard ratio, 0.94), was similar for grade 1 o…