Researchers have pinpointed just how much an unfavorable BMI measurement raises mortality risk among the overweight and obese (N Engl J Med. 2010;363:2211-2219). The CDC and the World Health Organization define normal BMI range as 18.5-24.9.

Data were pooled from 19 long-term studies of five to 28 years’ duration, excluding smokers and people with pre-existing illness to get a sharper picture of the impact of excess weight alone. The 1.46 million subjects were white adults, aged 19 to 84 years; median BMI was 26.2.

Healthy but overweight (BMI 25.0-29.9) women were 13% more likely to die during follow-up than were those with a BMI between 22.5 and 24.9.

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Compared with the 22.5-24.9 range, risk of death was 44% higher for obese (BMI >30.0) women and 88% higher for severely obese (BMI >35) women who did not exceed a BMI of 39.9. Participants with BMI of 40.0-49.9 had a 250% (2.5 times) higher risk of death than the 22.5-24.9 group. Results were broadly similar for men.

Overall, every five-unit increase in BMI translated to a 31% higher risk of death for men and women combined. The greater mortality risk for a BMI of 25 or more was observed in all age groups, but was more evident among those who were overweight or obese before age 50 years.