Weight loss may be influenced by joining a team.

A new study shows that people who shed at least 5% of their initial body weight during a weight loss competition were likely to be on the same teams. Those who said their teammates played a large role in their weight loss were more likely to lose a significant amount of weight.

The findings appear in Obesity.

Shows like The Biggest Loser often have team-, family-, or couples-based competitions that harness the power of peer influence when it comes to weight loss.

“People around us affect our health behaviors,” says researcher Tricia Leahey, PhD. She is with The Miriam Hospital’s Weight Control and Diabetes Research Center and is an assistant professor of psychiatry and human behavior at Alpert Medical School of Brown University in Providence, R.I.

This is true for healthy and unhealthy behaviors. “It could be quite beneficial if a bunch of friends that choose to lose weight make healthy food choices together, and hold each other accountable to those choices,” she says.

Team members can motivate one another to stay the course. “If someone is doing really well, it could influence the whole group,” Leahey says.

The findings are based on the results of the 2009 Shape Up Rhode Island campaign, a 12-week statewide, online weight loss competition. Participants competed against other teams for weight loss, physical activity, and the number of steps taken. The weight loss arm included 3,330 overweight or obese people on 987 teams. The teams had between five and 11 members.

Two of the study’s co-authors, Rajiv Kumar, MD and Brad M. Weinberg, MD, are co-founders of ShapeUp, Inc.

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There Is No ‘I’ in Team

People who lost at least 5% of their body weight, which is an amount that is thought to be significant in improving health, tended to be on the same teams. Those who reported a higher level of social influence by their teammates increased their odds of significant weight loss by 20%.

“This is really quite powerful,” Leahey tells WebMD. "We were surprised by the magnitude of the effect."

Team captains lost more weight than team members. This may be because they were more motivated and engaged in the contest.

Kevin Sloan is the acting psychology director at Beaumont Weight Control Center in Royal Oak, Mich. The findings mirror what he sees in his practice. “We find that when couples begin their weight loss journey together, they tend to do better. There is a lot of credence to the buddy concept,” he says.

Not everyone is a team player. “It is important to do a self-assessment before signing up, but this a good approach for some people who are joiners and do much better as part of a group,” he says.
Weight Loss Is Contagious

“People do better in a group because of the peer pressure,” says Louis Aronne, MD, founder and director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Center.

And “virtual” weight loss works, too. Groups can get together via the web. “Social support helps people to do better, and there are a variety of ways to accomplish it,” Aronne says.

Still, group dynamics can backfire. "When someone is not doing very well, sometimes that person gets pulled along and sometimes they don’t,” he says.