Money talks when it comes to motivating people to lose weight, a new study shows. And it doesn’t have to be a ton of cash. Just receiving $20 a month for losing 4 pounds—or having to hand over $20 for not losing the weight—was enough to encourage many people to stay the course, according to a research.

In the study, 100 employee volunteers who were considered obese (BMI between 30 and 39.9—if your BMI is between 25 and 29.9, you are in the healthy weight range.) were placed into one of four weight-loss groups: two with financial incentives(金钱激励) and two without.

Those people in the financial incentive groups who met their goal received $20 per month, while those who didn’t had to pay a penalty(罚款) of $20 into a larger bonus pool(奖池). Participants in the two incentive groups who completed the study were eligible to win this bonus pool when the study ended.

When all was said and done, those who were paid money for losing weight lost more and were more likely to complete the study. Specifically, 62 percent of those who got paid for losing weight each month stayed the course, compared with only 26 percent of those who had no opportunity to receive financial incentives. Among people in the incentive groups, weight loss was slightly more than 9 pounds, on average. In contrast, participants who did not receive money to lose weight lost an average of 2.3 pounds.

More study is needed to see how long these changes can last, one of the researchers Driver noted. “The real challenge is to make this research longer, and see if we can develop a sustainable financial incentive model that lasts for longer than one year,” he said.