Facebook is a popular site for people to share personal-fitness goals. But a recent study found publicizing the goals on social media doesn’t lead to a significant increase in exercising.

Sharing weekly exercise goals on Facebook often brought an outpouring of support from friends and family, the study found. But people who used the social-media site were less likely to set goals in the first place than others who kept their commitments to themselves. And while people who went public with their goals exercised a bit more than those who kept private, the difference wasn’t statistically significant.

“If you can’t get yourself to make a public commitment, you should at least make a private commitment,” says Paul Resnick, a professor at the University of Michigan School of Information and a co-author of the study. “They’re effective when we make them [public], but it’s a little scary to make them.”

The study was published in the proceedings from an Association of Computing Machinery conference in April on human factors in computing systems.

The randomized, controlled study lasted 12 weeks. It involved 165 obese people in the University of Michigan Medical System who each wore a Fitbit pedometer. Participants were divided into three groups: one whose goals and results were made public, another in which only goals were made public, and a group whose goals and results were kept private.

The group whose goals and results were made public increased their exercising by an average of 1,407 steps a day. That was greater than the 957-step average daily increase of those whose goals and results remained private. However, the variation among individual participants was so wide that the difference wasn’t statistically significant, the study said.

Participants who knew their exercise goals and results would be made public made fewer weekly commitments—in just 77 percent of the weeks. People who had only their goals shared, but not results, made commitments in 79 percent of the weeks. By contrast, people whose goals were private made commitments in 88 percent of the weeks.

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