A recent report1 on the associations between body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters) and risks of various chronic diseases in the Nurses' Health Study and the Health Professionals Follow-up Study contained 2 results that we find puzzling. First, the association between BMI and risk of "heart disease" in the Nurses' Health Study was much weaker than that implied for coronary heart disease (CHD) in 2 earlier reports from the same study.2,3 For example, whereas the 2 earlier reports had maximum relative risks of 3.3 and 3.6 (for participants with a BMI ≥29), the recent report had a maximum relative risk of just 1.7, even though this relative risk was for participants with a more extreme range of BMI values (≥35). (All 3 reports had comparable reference groups.) We estimate that while the average increase in risk for each 1-unit higher BMI was 10% to 12% in the earlier reports, in the recent report it appeared to be just 3% to 4%. Coronary heart disease is by far the most common form of heart disease in Western populations, so it is surprising that the association of BMI with risk of "heart disease" should have been so much weaker than that with the risk of CHD.
Whitlock G, Lewington S. Surprising Evidence About Associations Between Body Mass Index and Risks of Coronary Heart Disease and Stroke. Arch Intern Med. 2002;162(21):2490. doi: