Doctoral Candidate Finds Mortality Risk of Being Overweight are Underestimated

New research by Andrew Stokes, a doctoral student in demography and sociology in Penn Arts and Sciences, suggests that many obesity studies substantially underestimate the mortality risks associated with excess weight in the United States. His study “Using Maximum Weight to Redefine Body Mass Index Categories in Studies of The Mortality Risks of Obesity” was published in the March issue of the open-access journal Population Health Metrics.

Stokes used individuals’ highest BMI in life to predict mortality rates. He conducted the analyses using data from the National Health and Nutrition Examination Surveys of 1988-1994 and 1999-2004 linked to the National Death Index through 2006 on U.S. adults ages 50-84 who never smoked.  

In prior studies, the normal weight category combines data from low-risk, stable-weight individuals with high-risk individuals who have experienced weight loss. Use of weight histories makes it possible to separate the two groups and redefine the reference category as people who were a consistently normal weight throughout their lives

He found that the percentage of mortality attributable to overweight and obesity in this group was 33 percent when assessed using maximum BMI. The comparable figure obtained using BMI at the time of survey was substantially smaller at only 5 percent.

For the past five years Stokes has worked on projects related to obesity and diabetes with Samuel Preston, a professor of sociology at Penn, as part of a grant from the National Institute on Aging.

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