This NYT piece asks the question "How much does it cost not to go to the gym?" Note this is an economic article, not a health related one. (via Mises Blog)

Health club memberships offer a particularly clear case study, probably because they offer two opportunities for excess optimism. First, people overestimate the number of times they will make the effort to get to the treadmill or the weight room. Then they congratulate themselves for seeming to save money by buying an expensive gym membership that rewards frequent visitors.

Stefano DellaVigna, an assistant professor of economics at the University of California at Berkeley, and Ulrike Malmendier, an assistant professor of finance at Stanford, recently collected data at three health clubs in New England. Like many others, the clubs offer three basic membership plans. People can pay about $10 a visit, a monthly fee of about $70 or an annual fee of roughly $700.

Relatively few people pick the annual contract, leaving them with what seems like a fairly simple comparison. If they expect to go to the gym at least seven times a month — or about twice a week — the monthly package makes sense. Any less of a gym rat should pay $10 each visit.

This seems a good place to pause, set aside feelings of financial superiority and ask yourself how often you go to the gym. The answer for this overconfident consumer, who pays a flat monthly fee at his gym, is about once a week.

In the study, monthly members go about as often and, as a result, pay the equivalent of about $17 a visit. Only one in five members saved money by buying the monthly contract, the professors found when they studied the clubs' records. Over a six-month period, the average member would have saved more than $150 by paying for each visit.