Being Even Moderately Overweight Boosts Mortality Risk

"Excess body weight during midlife, including overweight, is associated with an increased risk of death," say researchers in the abstract for "Overweight, Obesity and Mortality in a Large Prospective Cohort of Persons 50 to 71 Years Old" in the Aug. 24 issue of The New England Journal of Medicine.

The study, which was supported by the Intramural Research Program of the National Cancer Institute, analyzed data drawn from 527,265 participants ages 50 to 71 in the NIH-AARP Diet and Health Study in 1995-96. Researchers defined overweight as having a body mass index, or BMI, of 25-29.9 and obesity as having a BMI of 30 or more. The study's reference group had a BMI of 23.5-24.9. Within the 10 years since the data were collected, 61,317 participants in the study had died.

"Whether moderate elevations in BMI (i.e., overweight) truly increase the risk of death is controversial," the researchers say. They analyzed data from the entire cohort and then sought to isolate the BMI factor by taking several steps. The researchers selected data on subjects who had not smoked and eliminated data on subjects who died early in the 10-year span because they might have had pre-existing conditions. In addition, this phase of the study used BMIs recorded by healthy subjects at age 50, "a time of life reflecting typical adult weight and largely unaffected by the onset of diagnosed disease," the report says.

During the 10-year study, for nonsmoking subjects who reportedly were healthy at age 50, the risk of death for people who were overweight increased by 20 percent to 40 percent compared with healthy nonsmokers in the reference group, and the risk of death increased by "two to at least three times" among people who were obese, says the report.

The researchers adjusted for variables including level of education, race or ethnicity, alcohol consumption and physical activity, "which allowed us to minimize the potential for confounding by these factors," say the authors. In their conclusion, the researchers note, "Many of the participants, who were 50 to 71 years old at baseline, are from the baby-boomer generation. Much has been written recently about the rise in obesity -- and its medical consequences -- in this segment of the population. Even against the background of advances in the management of obesity-related chronic diseases in the past few decades, our findings suggest that adiposity, including overweight, is associated with an increased risk of death."

Two related articles in this NEJM issue are "Body-Mass Index and Mortality in Korean Men and Women," for which the abstract is available without registering, and "Overweight and Mortality Among Baby Boomers -- Now We're Getting Personal," for which an extract also is available.