May 10, 2016

expert reaction to BMI and risk of death

The relationship between body mass index (BMI) and mortality is the subject of a paper published in the Journal of the American Medical Association which reports that the BMI associated with the lowest risk of death has increased by 3.3 from studies in 1976-1978 to 2003-2008.

Prof. Naveed Sattar, Professor of Metabolic Medicine at the University of Glasgow, said:

“These data are of interest but they do not change advice we have been giving on obesity and its treatment and prevention. In recent years, as populations become more obese and with wider availability of cheap preventative medications many more such individuals are likely to be better treated for abnormal blood pressure, abnormal cholesterol and, if also present, type 2 diabetes, leading in turn to lower death risks. In other words, the current findings do not mean that being overweight is protecting you from death, far from it – rather, many confounding factors may give the current result and we know from many other studies that being overweight or obese does increase mortality risks, in the same way that it increases risk for many other conditions. We also know from other studies that lower calorie intake increases life expectancy. So it’s a complex picture.

“The present analyses are not optimal and it would be wrong to conclude that we need to redefine obesity cut-offs based on these data. Obesity and overweight categories also signal risks for many diseases, such as type 2 diabetes, liver disease, cancers, sleeping problems, multiple pregnancy complications, to name but a few, many of which we can manage much better these days but of course such complications also impair quality of life, impair self-esteem, and increase health costs for societies. Yes, with modern medicines we can help people with risk factors such as obesity live longer than they would have in the past, but that does not mean we should also redefine obesity cut-offs. We need a holistic view on obesity and societies should make it easier for individuals to make healthier lifestyle choices.”

‘Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013’ by Shoaib Afzal et al. published in JAMA on Tuesday 10 May 2016. 

Declared interests

Prof. Sattar was senior author on a trial which was funded by Coca-Cola on a placebo-controlled RCT of a novel flavonoid rich beverage – the trial was negative.