Correlation, Causation, and Having a Gym Next Door

“Having a gym nearby does help us to lose weight, suggests new research.” So says Medical News Today. This bit of classic click bait for weight loss season comes from Lancet Public Health. It’s an observational study of the correlation between a person’s risk of obesity and their home address. The authors found that people living near a gym and other fitness facilities have less body fat, lower BMIs, and smaller waists.

The researchers also found a weak correlation between living near a fast food outlet and obesity risk.

Reverse Causation

The investigators are eager to leap to translating this observation into policy. Lead author Kate Mason says:

The results of our study suggest that increasing access to local physical activity facilities and, possibly, reducing access to fast-food close to residential areas could reduce overweight and obesity at the population level.

Yet, in her paper, she concedes that reverse causation is a serious issue. In other words, people who are more fit and trim might choose to live in neighborhoods with plenty of fitness facilities nearby. And fitness facilities might choose to locate in places with plenty of eager customers. Duh.

Learning from Past Mistakes

We have plenty of reasons to believe that where a person lives can affect their health. But it’s also clear that this relationship is complicated.

For example, we learned from the Healthy Food Financing Initiative that simply plunking down supermarkets in the middle of a food desert doesn’t have much of an effect. Likewise, Los Angeles learned that banning new fast food outlets had no impact on obesity risks.

So yes, attention to creating healthy places to live is important. But simply plunking down a lot of fitness clubs might not be a magic answer. Let’s move thoughtfully and learn as we go.

Click here for the study, here for the paired commentary, and here for more from MedPage Today.

Dayton Gym Club, photograph © vistavision / flickr

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January 3, 2018