All you need to read in the other general journalsBMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d1622 (Published 16 March 2011) Cite this as: BMJ 2011;342:d1622
Keep measuring body mass index
Measures of body fat—body mass index, waist to hip ratio, and waist circumference—are a major determinant of cardiovascular disease. Higher values for all three indicate a higher risk of heart attacks and strokes for middle aged and older adults, and some tools for predicting these events include at least one measure of body fat. They probably shouldn’t, say researchers. An analysis combining data from 58 different cohorts suggests measures of body fat, alone or in combination, add very little to formal risk prediction using age, sex, blood pressure, history of diabetes, smoking, and lipids⇓.
This is a setback for resource poor countries hoping to dispense with expensive cholesterol tests and use body mass index instead, says a linked comment (doi:10.1016/S0140-6736(11)60239-0). When added to other risk factors, body mass index had a fraction of the predictive power of key serum lipids in this analysis, the fourth blockbuster cohort study in recent years to look at the relation between body fat and chronic diseases or death.
That doesn’t mean we should stop weighing and measuring people, says the comment. Excess body fat is a useful (and treatable) early warning of likely trouble to come, mediated by the effect of fat on blood pressure, lipids, and glucose metabolism.
Unlike some others, the new study found that the association between fat and cardiovascular disease was equally powerful for all three measures (around 25% more disease for each standard deviation increase after adjustments for age, sex, and smoking). Moves to replace body mass index with waist to hip ratio as the metric of choice may be premature, says the comment. Waist to hip ratios are notoriously hard to get right in overweight or obese adults.