Researchers performed a randomized, controlled trial of obese employees at Children's Hospital of Philadelphia to see whether offering money to a group or to individuals resulted in greater weight loss. Thirty-five employees were assigned to the control group; 35 were assigned to receive $100 each per month for meeting or bettering their weight loss goals; and 35 were assigned to receive $500 per month, which was split within five-person subgroups. For the group incentive, money that would have gone to participants who did not meet their weight loss goals was instead divided equally among those who did. All study participants were weighed monthly over 24 weeks. Study results were published Tuesday in Annals of Internal Medicine.
The study found that at 24 weeks, employees who were offered a group incentive lost more weight than both controls (mean between-group difference, 4.4 kg; P<0.001) and those offered an individual incentive (mean between-group difference, 3.2 kg; P=0.008). Employees in the group-incentive arm also maintained greater weight loss than controls, but not individual-incentive participants, 12 weeks after the incentives ended.
The authors noted that their study was done at only one institution and that its follow-up was short. However, they concluded that in this trial of an employer-based intervention, group financial incentives worked better than individual ones for weight loss. Their results demonstrate that "varying features of incentive design can lead to important differences in the costs of incentives and their effects on health outcome," they wrote.