The Risks of Assuming We Know What Causes Obesity

Oscar Wilde long ago warned about the risks of assuming. But that doesn’t put a dent in some deeply held assumptions about what causes obesity. We lived through decades of nutrition policy that assumed excess fat in the diet was responsible for obesity and a host of other chronic diseases. Now we know that those assumptions did not hold up under scrutiny and may have made things worse.

We widely assume that junk food is readily identifiable and responsible for obesity. But David Just and Brian Wansink are reporting that their analysis of NHANES data finds no association among BMI and consumption of junk food: fast food, soft drinks, and candy. They may have a point, since many foods assumed to be healthy (yogurt comes to mind) are being sold in forms that have all the characteristics of junk food. Unfortunately, Just and Wansink are busy issuing press releases about a study that has yet to appear in its peer-reviewed form. So we are left with sensational headlines and a pre-publication manuscript that together serve only to muddy the waters.

More thoughtful analysis and discussions appear in the Atlantic, the Chicago Policy Review, and the National Bureau of Economic Research (NBER) on the subject of food deserts as a potential cause of obesity. They note the popular belief that food deserts are a key driver of poor diets and that efforts to improve access to healthy foods will correct the problem. But their analysis indicates that such efforts will have little effect.

The graphic from the Obesity Society above on the right illustrates the complexity what we are dealing with. Potential contributors to obesity are many and our understanding of this disease is incomplete. Simplistic assumptions are inherently as misleading as they are appealing.

Click here for the manuscript by Just and Wansink and here for a sample of the headlines they’ve generated. Click here for more on food deserts from the Atlantic, here for more from the Chicago Policy Review, and here for the NBER manuscript.

Donkey, photograph © myri bonnie / flickr

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November 11, 2015