About one-third of U.S. adults are overweight. Although suspected, the association between excessive weight and risk of death has not been demonstrated with certainty. This may be partly because illnesses prior to death often cause weight loss, so that by the time of death patients who were formerly overweight have a normal body mass index (BMI). Previous studies, therefore, may have downplayed the significance of excessive weight on mortality risk.
A new study tracked the weight history of 225,072 men and women to examine the risks of all-cause and cause-specific death associated with overweight and obesity. The study population included women enrolled in the Nurses' Health Study and Nurses' Health Study II and men in the Health Professionals Follow-Up Study.
Body weight was self-reported every two years during a 16-year period, and BMI was calculated and categorized as underweight, normal weight, overweight, obese I, or obese II. The main outcome studied was death from any cause. For men, there was a significant association between maximum BMI and mortality in the overweight, obese I, and obese II categories. Among women, there was an association between maximum BMI and mortality in the underweight, overweight, obese I, and obese II categories. The strongest association between maximum BMI and mortality was found to be attributable to cardiovascular disease.
The researchers also discovered that those who lost a significant amount of weight after reaching their maximum BMI had a higher mortality risk than those who were currently at their maximum BMI. This finding, however, may reflect weight loss due to illness. The study demonstrated that people who maintain an optimal BMI, which ranges from 18.5 to 24.9 kg/m2, have the lowest mortality risk.
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