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Letters
August 3, 2005

Underweight, Overweight, Obesity, and Excess Deaths

JAMA. 2005;294(5):551-553. doi:10.1001/jama.294.5.551-b

To the Editor: In their study of body weight and mortality, Dr Flegal and colleagues1 demonstrated that, relative to a BMI between 18.5 and less than 25, a low BMI (<18.5) was associated with higher mortality rates, a moderately increased BMI (25 to <30) with lower mortality rates, and a high BMI (≥30) with higher mortality rates. However, the conclusion that being underweight increases mortality while being overweight (but not obese) decreases mortality does not take into account critical problems with the use of BMI as a measure of body habitus. A moderately increased BMI does not distinguish between muscularity and increased total body fat or its distribution. Among adults with a BMI in the range of 25 to 34.9, public health guidelines specifically indicate that waist circumference must also be taken into account to assess health risks, since BMI in this range is an inadequate biomarker of body fat.2 Physical activity, an important covariate,3 was not considered in their analysis.

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