Willpower apparently can be bought.
The chance to win or lose $20 dollars a month enticed people in a yearlong study to drop an average of nine pounds.
That's four times more weight than others who were not offered a cash reward.
The Mayo Clinic study is the longest test yet of financial incentives for weight loss.
Many employers offer money to try to change bad habits such as not exercising or smoking, but other studies found this doesn't work for long.
Mayo researchers think their approach is successful because people are not only rewarded for losing weight, but penalized financially if they don't shed pounds.
Participants could also recoup lost money if they fell off the diet wagon and later repented.