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Dieters Lose Weight When Reward Is Cash

When Cash Is the Carrot, Obese People Lose More Weight, Study Shows
WebMD Health News
Reviewed by Louise Chang, MD

Dec. 9, 2008 -- Cash diets help people achieve weight loss goals, a Wharton School/VA study shows.

The cabbage in these diets isn't a vegetable. It's cold cash, paid -- and sometimes lost -- on a daily basis.

Surprisingly, it's the immediacy of the payoff and not the dollar amount that matters, shows the study by Kevin G. Volpp, MD, PhD, director for health incentives at the University of Pennsylvania's Wharton School and the Philadelphia VA Medical Center, and colleagues.

"Behavior-change efforts are often futile because those changes might help you sometime in the future, but the average person has trouble making that future reward relevant today," Volpp tells WebMD. "Cash reward programs offer a chance to change behavior and get a reward right now."

Offering cash rewards for weight loss isn't a new idea, notes Martin Binks, PhD, director of behavioral health at the Duke Diet and Fitness Center in Durham, N.C. Binks was not involved in the Volpp study.

"Reward programs can be very effective in the short term," Binks tells WebMD. "But we see 750 new people a day at our center -- and 750 more who return for help losing weight. Those who lose weight in the long term really take this to a deeper personal level. They make the shift to connecting their everyday actions to broader personal goals."

Cash for Weight Loss

Most of us, Volpp says, "heavily discount the future." Human nature makes it hard for us to give up something today in hopes of a far-off reward. But we're easily motivated to act quickly by rewards dangled right in front of us.

To demonstrate the point, Volpp and colleagues designed two weight loss schemes and tested them on 57 obese, 30- to 40-year-old men and women who wanted to lose weight.

Their goal: Lose 16 pounds in 16 weeks. Every morning, they weighed themselves and called in the result to the researchers. At the end of each month, they went in for a weigh-in.

Participants randomly assigned to the first scheme got a lottery number. Every day, they had a 1-in-5 chance of winning $3 and a 1-in-100 chance of winning $100. They got a payout at the end of each month -- but only if they met their weight loss goal of losing a pound a week.

"They got fairly frequent positive rewards," Volpp says. "The particular design of this is important, because people win fairly often, so they know it is a real lottery. And then they have a chance of a bigger prize that serves as a carrot to move forward."

Those assigned to the "deposit contract" group had to put up their own money. They had to give the researchers a self-selected amount, from 1 cent to $3, for every day of the study. They got the money back -- sweetened by a matching amount from the researchers -- only if they met their monthly goal. At the end of the study, those who lost at least 20 pounds got to split the money forfeited by those who did not meet their goals.

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