What a few extra pounds can—and can't—do for your health

December 1, 2007

An analysis of mortality and body mass index (BMI) data from 1971 through 2000 revealed that while being either underweight (BMI 18.5 or less) or obese (BMI 30 to 35 or greater) could endanger your life, just being overweight (BMI 25 to less than 30) did not. On the contrary, it turned out that overweight people had lower mortality rates from any cause than people who managed to maintain a so-called normal weight (BMI 18.5 to less than 25).

An analysis of mortality and body mass index (BMI) data from 1971 through 2000 revealed that while being either underweight (BMI 18.5 or less) or obese (BMI 30 to 35 or greater) could endanger your life, just being overweight (BMI 25 to less than 30) did not. On the contrary, it turned out that overweight people had lower mortality rates from any cause than people who managed to maintain a so-called normal weight (BMI 18.5 to less than 25).1

Now a refined analysis of the data enables the same researchers to be more specific about the advantages-and risks-of being overweight.2 In the new study, researchers examined cause-specific excess deaths in the year 2004 from cardiovascular disease (CVD), cancer, and all other causes, and correlated these with BMI categories. The analysis showed that

  • Overweight people do have an advantage. They have lower overall death rates because they are less likely to die from infectious disease or other causes not related to cancer or CVD and no more likely to die from cancer or CVD. However, overweight is associated with significantly increased mortality from diabetes and kidney disease combined.
  • Underweight people run a significantly increased risk of dying from nonCVD and noncancer causes but are not more likely to succumb to cancer or CVD.
  • Significantly higher mortality rates among the obese are primarily attributable to CVD. Obesity is also associated with increased mortality from cancers considered obesity-related and from diabetes and kidney disease combined. Obesity was not associated with higher mortality rates from other cancers.

Where does all this leave the primary care practitioner, puzzling over what advice to give patients about maintaining a healthy weight? Clearly, obese patients should be counseled to lose weight, and underweight patients to try to put on a few pounds. And as for your "overweight" patients? Perhaps it's time to revise that definition.

1. Flegal KM, Graubard BI, Williamson DF, et al. Excess deaths associated with underweight, overweight, and obesity.JAMA. 2005;293(15):1861-1867.
2. Flegal KM, Graubard BL, Williamson DF, et al. Cause-specific excess deaths associated with underweight, overweight, and obesity. JAMA. 2007; 298(17):2028-2037.