Jogging Beats Genes for Obesity? Not Exactly

Facts are stubborn. So, too, is an entrenched bias. The bias that obesity is a simple matter of choice runs especially deep. Thus it creeps into headlines and even scientific journals. A new study in PLOS Genetics provides a vivid case in point. Unwarranted causal language in a paper flows through to a press release. And then, we have a flood of headlines with false claims about jogging beating the effects of obesity genes.

Correlation, Attenuation, Cause, and Effect

Wan-Yu Lin and colleagues conducted a study of the correlation between genetic risk scores for obesity, self-reported exercise, and measures of obesity. They found that self-reports of exercise correlate with less obesity, even in people with significant genetic risks for it. They also found that the association was stronger for some forms of exercise than others. For example, jogging came out on the top of their list.

So the authors claimed – in the title of their study – that exercise “attenuates” the effects of genes on obesity. Note that attenuate means to reduce an effect. Yep, the data is all about correlations. But the researchers are claiming a discovery of cause and effect.

On top of this unjustified use of a causality claim, we have a press release from PLOS adding to the hype. “Jogging and five other exercises ward off weight gain,” it says.

So it’s easy for Newsweek to justify a sensational headline about how exercise “beats the effects of obesity genes.” The only trouble is that it’s a false.

On top of the false assumption that correlation proves causation, we have another problem. Exercise doesn’t eliminate the genetic risk of obesity. It merely reduces the size of that risk. The risk is still there. These data suggest a possibility for reducing it. Not for eliminating it.

Tropes Versus Truth

“Genes are not destiny” is a popular trope. It’s a way to suggest that you can overcome the gene pool you inherit. Sometimes it’s completely true. Sometimes not so much.

Overcoming obesity with exercise is a nice thought. Exercise is a good idea with many health benefits. However, for weight outcomes, you can’t outrun a bad diet. And thus, false claims and exaggerations are poor tools for promoting health. The lies come back to bite.

The truth is that obesity is highly heritable. Genes explain about 70 percent of an individual’s risk for obesity. The rate of obesity in the population has gone up because our environment has changed in many ways to promote it.

Our genes set the table for obesity. Then our environment serves it up. Given that, we must choose what to do about it. The options are many. But they’re far from perfect. So we do the best we can.

Click here for the study, here for the press release, and here for the coverage from Newsweek.

Morning Jog, photograph © Patrick Down / flickr

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August 5, 2019