This Is Why You Don't Go to the Gym

We can't keep our own fitness promises for the same reason that addicts are addicts and Congress can't pass deficit reduction

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Every January, millions of Americans, brimming with optimism and a little extra belly from the holidays, commemorate the new year by making an unfamiliar urban trek. They go to the gym.

One in eight new members join their fitness club in January, and many gyms see a traffic surge of 30 to 50 percent in the first few weeks of the year. Stop by your local gym today, and the ellipticals will be flush with flush new faces. But next thing you know, it will be April, our gym cards will be mocking us from our wallets, and our tummies will have sprouted, on cue with the tree buds.

Economists make and break gym promises just like the rest of us. And, as they're considerably more likely to run statistical regressions on their personal lives, there's a healthy academic literature about going to the gym. Here's what economics can teach us about fitness and the fitness industry.


People are way too optimistic about their willpower to work out, Stefano Dellavigna and Ulrike Malmendier concluded in their famous paper "Paying Not to Go to the Gym." In the study, members were offered a $10-per-visit package or a monthly contract worth $70. More chose the monthly contract and only went to the gym four times a month. As a result, they paid 70 percent more per visit than they would have under the plan they rejected. Why? Because people are too optimistic that they can become gym rats, which would make the monthly package "worth it." Silly them.

You might call this behavior "laziness." Economists prefer "hyperbolic discounting." This is the theory that we pay more attention to our short-term well-being and "discount" rewards that might come further down the road. Think of a small reward in the distant future, like taking a nap three weeks from now. Doesn't hold much appeal, does it? But when the small reward is imminent -- Take a nap right now? Woo hoo! -- it's considerably more attractive. Given the choice between small/soon rewards versus larger/later benefits, we'll take the former. Hyperbolic discounting helps to explain why Congress can't pass deficit reduction, why drug addicts stay addicts, why debtors don't pay off their bills, and why you keep telling yourself that the right day for exercise is always "tomorrow."

The other problem with sustaining the motivation to work out is that ... well, motivation is exhausting! According to the theory of decision fatigue, the simple act of making any decision depletes us of a limited store of willpower. Exercise isn't just an investment of time, it's also a choice -- and a difficult, even exhausting choice for people whose daily habits don't involve running and lifting.


Think about what you're paying for at the gym. The machines, the free weights, the televisions, the shower. But aren't you also investing in motivation? A membership is different from a one-time purchase. It's also a promise that you expect your future self to uphold. But too often, a membership isn't enough to keep us at the gym. Maybe the nudge we need is just ... money.

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Derek Thompson is a senior editor at The Atlantic, where he writes about economics, labor markets, and the entertainment business.

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