From Science World Report:
The participants were told to achieve the goal of losing 4 pounds per month up to a predetermined goal weight. The researchers kept track of their body weight every month for almost one year. The researchers told the participants in the incentive groups that they would receive $20 per month if they achieved the goal. And those who failed to achieve the goal would need to pay $20 each month that gets into the bonus pool. Participants in both incentive groups who finished the study were entitled to win the pool by lottery.
The researchers noticed that 62 percent of the participants in the incentive group achieved the goal, while just 26 percent from the non-incentive group hit the target. The mean weight loss of participants from the incentive group was 9.08 pounds and the mean weight loss for the non incentive group was 2.34 pounds.
"The take-home message is that sustained weight loss can be achieved by financial incentives," lead author Steven Driver, M.D., an internal medicine resident at Mayo Clinic, said in a press statement. "The financial incentives can improve results, and improve compliance and adherence."