A preliminary study suggests that economic incentives appear to be effective for achieving short-term weight loss, according to a report in the December 10 issue of JAMA.

"In 2004, 71 percent of U.S. adults were overweight or obese according to standard definitions, and at present obesity falls just behind smoking as a preventable cause of premature death," the authors provide as background information. "Although many variables contribute to the increase in obesity prevalence in the United States, behavioral economics has identified several patterns of behavior that help explain why people engage in self-destructive behavior, including the tendency to put disproportionate emphasis on immediate gratifications, such as the pleasure of eating, relative to the much smaller emphasis put on delayed benefits, such as enjoying good health." The author suggest "new strategies are needed to help reduce the rate of obesity in the U.S. population."

Kevin G. Volpp, M.D., Ph.D., from the University of Pennsylvania School of Medicine and the Wharton School, VA Center for Health Equity Research and Promotion, Philadelphia, and colleagues, designed two incentive-based approaches for losing weight. One was a lottery-based group in which the participants played a lottery and received the earnings if they achieved or lost more than the target weight and the other was a deposit contract condition in which the participants invested their own money, which they lost if they failed to achieve weight goals. Fifty-seven participants were randomly assigned to participate in either a weight-monitoring program involving monthly weigh-ins, or the same program with one of the two financial incentive plans (deposit contract or lottery). All participants had a goal weight loss of 16-pounds over 16 weeks.

"The incentive groups lost significantly more weight than the control group (mean [average] 3.9 pounds)," the authors report. "Compared with the control group, the lottery group lost a mean of 13.1 pounds and the deposit contract group lost a mean of 14.0 pounds. About half of those in both incentive groups met the 16-pound target weight loss: 47.4 percent in the deposit contract group and 52.6 percent in the lottery group, whereas 10.5 percent in the control group met the 16-pound target." As for the incentives: "Over the course of the 16-week study, the average amount of money earned in weight loss incentives was $378.49 in the deposit contract condition and $272.80 in the lottery condition." The authors note that the study participants in both of the incentive groups gained weight between the end of the weight loss incentive intervention and the end of 7 months, but still weighed less at 7 months than they did at the start of the study. 

"In conclusion, incentive approaches based on behavioral economic concepts appear to be highly effective in inducing initial weight loss. However, this weight loss was not fully sustained and further work is needed to test the effectiveness and cost-effectiveness of these approaches in achieving sustained weight loss," the authors write.