Researchers at the University of Pennsylvania studied how cash incentives influenced weight loss among 57 people who were obese but otherwise healthy. One group of dieters was given $3 a day plus additional matching funds for meeting weight loss goals, meaning they could earn up to an extra $168 during a four-week period. A second group was eligible to compete in a cash lottery for $10 to $100 a day during the study period if they achieved weight loss goals. A third control group simply attended monthly weigh-in sessions. At the end of 16 weeks, the dieters in the lottery group had lost an average of 13.1 pounds each, while those in the matching-funds group had lost an average of 14 pounds each, compared to just 3.9 pounds in the control group.