Overlooking Much of Obesity’s Impact on Death Rates

A new study in the Proceedings of the National Academies of Sciences reveals that scientists may be overlooking more than a quarter of obesity’s impact on death rates. The lead author, Andrew Stokes of Boston University, explains:

The risks of obesity are obscured in prior research because most of the studies only incorporate information on weight at a single point in time. The simple step of incorporating weight history clarifies the risks of obesity and shows that they are much higher than appreciated.

The notion of considering a person’s whole history is something that has been standard practice in assessing the risks of smoking for more than a half century. In the case of obesity, the authors point out that weight history is especially important because, ironically, ill health that results from obesity can lead to weight loss before it progresses to a premature death.

In the case of obesity, the authors showed that mortality for people with a history of obesity is more than double that for people who have never had obesity. The figure on the right splits out people with a normal BMI into three distinct groups: people with no history of excess weight, people who formerly had excess weight, but not obesity, and people with a history of obesity.

Unfortunately, some of the reporting on this study is missing a key point. The misleading headlines are saying that “even after weight loss, obesity can reduce lifespan.” In fact, what the researchers found was that illness associated with obesity was leading to weight loss and hastening death. This study did not in any way evaluate the effect of intentional or therapeutic weight loss on mortality.

Like so many other aspects of obesity, putting a precise number on the excess deaths it causes is far from simple.

Click here for more from Boston University and here for the study in PNAS.

Golden Crypt, photograph © Graniers / flickr

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January 6, 2016