This reinforcement intervention had substantial benefits for decreasing body weight. On average, patients assigned to the reinforcement condition lost 6.1 kg versus 2.7 kg for those in a known effective weight loss intervention. Weight loss in the LEARN+supportive counseling condition was similar to that in other studies of this approach,7-9
and adding reinforcement improved significantly upon these effects. Although these patients were predominately female, they lost as much over 12 weeks as the primarily male sample in the Volpp et al.5
study lost over 16 weeks, perhaps because of the inclusion of an effective platform intervention.
Nearly two-thirds of patients in this reinforcement condition lost 5% or more of baseline body weight. Percent reduction in body weight was significantly predictive of reductions in total cholesterol and 24-hour heart rate. These results suggest that even short-term reductions in weight can result in clinically important health benefits, and this level of weight loss reduces risks of developing diabetes, heart disease and stroke.11
A concern often raised about reinforcement-based interventions is that effects may not persist beyond the duration of treatment. We were not able to evaluate post-intervention effects in this preliminary trial, but to achieve long-term benefits, one first needs to achieve initial success. The improved retention and weight loss in this reinforcement intervention suggest that reinforcement should be applied during early stages of weight loss efforts. Whether extended benefits are best sustained by continued reinforcement, modifications to reinforcement procedures, or other interventions remains to be determined.
Additional costs of including reinforcement were relatively modest. On average, patients earned less than $14 per week in the reinforcement conditions, about half that provided in Volpp et al.'s5
study. Although larger scale studies are needed to understand minimal costs necessary and cost-effectiveness of adding reinforcement to weight loss treatments, studies in other populations find prize-based interventions are cost-effective.12
Limitations include the lack of long-term follow-up and the inability to report upon comparative efficacy with other reinforcement interventions. Although follow-up participation was high overall (93%), some patients declined ambulatory BP monitoring (n=13) or biochemical tests (n=3), limiting our ability to detect all but the most robust effects of weight loss on clinical parameters.
Strengths of this study include the integration of reinforcement with a known effective weight loss intervention. The two conditions were controlled with respect to frequency and intensity of expected therapist contact, and the reinforcement condition greatly enhanced treatment participation-- a substantial concern in weight loss treatments10
-- and it improved outcomes. This work expands our understanding of how financial incentives can contribute to weight loss. Consistent with the behavioral economic literature showing that small frequent reinforcers with the chance of large payoffs can substantially impact behavior,13
these data show that offering mainly low-cost reinforcers but a small chance of winning a valuable prize is efficacious in improving weight loss. Given the simplicity and modest costs associated with this approach, prize-based reinforcement appears to be a promising approach to enhance weight loss.