Mortality Risk of Obesity Underestimated?

Researchers have established that obesity is associated with increased mortality risk. However, a study suggests that the severity of this risk may have been underestimated.

Published in Population Health Metrics (2014; doi:10.1186/1478-7954-12-6), the study looked at mortality and body mass index in nonsmoking adults aged 50–84. Data was pulled from the National Health and Nutrition Examination Surveys (1988–1994 and 1999–2004) and linked to the National Death Index through 2006.

“Using maximum BMI, hazard ratios for overweight (BMI, 25.0–29.9 kilogram/meter2), obese class 1 (BMI, 30.0–34.9 kg/m2) and obese class 2 (BMI, 35.0 kg/m2 and above) relative to normal weight (BMI, 18.5–24.9 kg/m2) were 1.28, 1.67, and 2.15, respectively,” explained study author and doctoral candidate Andrew Stokes. “The percentage
of mortality attributable to overweight and obesity among never-smoking adults ages 50–84 was 33% when assessed using maximum BMI. The comparable figure obtained using BMI at time of survey was substantially smaller at 5%. The discrepancy is explained by the fact that when using BMI
at time of survey, the normal category combines low-risk stable-weight individuals with high-risk individuals that have experienced weight loss. In contrast, only the low-risk stable-weight group is categorized as normal weight using maximum BMI.”

The bottom line?

“Use of maximum BMI reveals that estimates based on BMI at the time of survey may substantially underestimate the mortality burden associated with excess weight in the U.S.,” Stokes warned.