OBJECTIVES: To examine whether (a) an obesity treatment involving financial incentives yields higher levels of extrinsic motivation for weight management compared to an identical intervention without incentives, (b) extrinsic motivation for weight management mediates, or accounts for, the difference in weight loss outcomes between the two interventions, and (c) there is any evidence that financial incentives and associated extrinsic motivation "crowd out" intrinsic motivation for weight control.
METHODS: Participants (N=153, 80.4% Female; BMI = 33.2 ± 5.9) were randomly assigned to a 3-month Web-based behavioral weight loss program (WBWL) or the same program plus small financial incentives delivered consistent with behavioral economics and behavior change theories (WBWL+$). Weight was objectively assessed at baseline, post-treatment (month 3), and after a 9-month no-treatment follow-up phase (month 12). Intrinsic and extrinsic motivation for weight management were assessed at months 3 and 12 using a modified version of the Treatment Self-Regulation Questionnaire, with questions added to specifically target extrinsic motivation related to incentives.
RESULTS: Compared to WBWL alone, WBWL+$ had better weight loss and higher levels of both extrinsic intrinsic motivation for weight management (p's≤.02). Moreover, during the no-treatment follow-up phase, the trajectories of weight regain did not significantly differ between WBWL and WBWL+$ (p=.58). Extrinsic motivation was not a significant mediator of treatment outcomes.
CONCLUSIONS: Modest financial incentives delivered consistent with behavioral economics and behavior change theories do not undermine intrinsic motivation for weight management during obesity treatment; in fact, they yield higher levels of both extrinsic and intrinsic motivation. Additional research is needed to better understand the mechanisms by which incentives improve outcomes in health behavior change interventions.
