Russian Auto Mechanic

Looking Under the Hood in Nutrition and Obesity

Looking under the hood is a messy business, whether you’re doing it literally with you car or figuratively with nutrition and obesity research. It’s much easier to take glib assurances at face value. But ignoring deeper problems in either case can be costly. In a thoughtful commentary published by the New York Times, Aaron Carroll observes:

We have, for too long, made decisive proclamations based on research that did not support them. (Remember when butter and fortified margarine was its own food group?) It was inevitable that some of those assurances would need to be retracted or amended. But now, we have gotten to a point where food has become ideological, and where motives are questioned based on results and not methods.

In this context, perspectives from two new studies in the International Journal of Obesity are especially valuable. The first, by Andrada Ivanescu and colleagues, dives deep into the methods for modeling risk in nutrition and obesity research. They shine a light on the problem of applying models for risk without adequately accounting for the inevitable loss of predictive validity that occurs across multiple datasets. Because this flaw can reduce the validity of a model almost to zero and because this flaw is often overlooked, the literature on obesity is rich with publications that misrepresent what is actually known about obesity risk factors.

The other study brings some real numbers to a problem that researchers have suspected for a long time. In randomized, controlled studies of obesity treatment, the control arm is almost never a true placebo. People may get a sham surgery, intensive behavioral therapy, or other interventions that have a real effect. John Dawson and colleagues showed that every kilogram that people in a control group loses will diminish the treatment effect of the treatment being tested by almost a third of a kilogram.

These are but two examples of ways we can be led to accept appealing but false conclusions in nutrition and obesity research. The only real protection comes from rigorous peer review and a critical mind.

Click here to read the study by Ivanescu and here to read the study by Dawson.

Auto Mechanic, photograph © Misha Maslennikov / flickr

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October 14, 2015