Obesity and Risk of Death in EuropeansTuesday, November 18, 2008
This week’s New England Journal of Medicine, features an article by Tobias Pischon on behalf of the EPIC (European Prospective Investigation into Cancer and Nutrition) investigators on the relationship between BMI, waist circumference, waist-to-hip ratio and mortality.
To me, this paper is of considerable interest – not least, because Tobias was one of my students back in Germany, who did his MD thesis on the effect of salt intake and obesity on chronic kidney transplant rejection under my supervision.
Of course, this paper also deals with a topic that I have often blogged about – i.e. the relationship between anthropometric measures and morbidity and mortality.
Pischon and colleagues studied 359,387 participants from nine countries during a mean follow-up of 9.7 years. After adjustments for age, educational level, smoking status, alcohol consumption, and physical activity, the lowest risks of death related to BMI were observed at a BMI of 25.3 for men and 24.3 for women.
After adjustment for BMI, relative risks among men and women in the highest quintile of waist circumference were 2.05 and 1.78, respectively, and in the highest quintile of waist-to-hip ratio, the relative risks were 1.68 and 1.51, respectively.
BMI remained significantly associated with the risk of death in models that included waist circumference or waist-to-hip ratio (P<0.001).
This study, essentially confirms what was already known, namely that the impact of excess body fat on mortality depends not only on the amount of excess fat (BMI) but also on its distribution (waist circumerence, waist-to-hip ratio).
Importantly, the measures of fat distribution are predictive of risk even in normal weight individuals with lower BMI’s, which challenges the use of cutoff points to define abdominal obesity.
On the other hand, as BMI increases, measuring fat distribution adds little to determining obesity-related risk. (which is why obesity guidelines do not recommend measuring waist cirumference in individuals with a BMI>40).