Financial Incentives for Longer-Term Weight Loss: A Randomized Controlled Trial
Posted: 6 Jul 2011 Last revised: 21 Jul 2012
Date Written: June 1, 2010
BackgroundAlthough previous efforts to use incentives to promote weight loss yielded successful results over a 16-week period, participants rapidly regained weight when incentives were removed (Volpp et al., JAMA, 2008). The purpose of this study was to evaluate the effectiveness of a weight loss intervention examining the sustainability of financial incentives using a deposit contract designed to augment motivation utilizing loss aversion in achieving longer-term weight loss and the robustness of these findings to the framing of the intervention.
MethodThis study was a 3-arm randomized controlled trial (N=66) of financial incentives for weight loss among veterans at the Philadelphia Veterans Affairs Medical Center who had BMIs between 30-40, were between 30 and 70 years old, stable medically, and able to consent. All participants first underwent a 24-week weight loss phase during which they were given a weight loss goal of 1 pound per week, followed by an 8-week maintenance phase. Participants were randomized to either usual care (weigh-ins once a month) or one of two financial incentive arms. Both incentive arms used deposit contracts (DC) in which participants put their own money at risk (matched 1:1 by the study) which they would forfeit if they failed to lose weight. In the DC1 and control conditions, the first 24 weeks of the study were framed as the ‘weight loss period’; the final 2 months were framed as the ‘maintenance of weight loss period’. In DC2, there was no explicit distinction between the two periods of the study. Approximately 9 months after the end of the trial, participants came in for follow-up weigh-ins. All results were analyzed using intention-to-treat analysis of variance models. The primary outcome measure was weight loss after 32 weeks. Recruitment took place from June 2008 – September 2008, with follow-up concluding in January 2010.
ResultsOver the course of the 32-week study, there were no differences in weight loss between the two financial incentive arms (p=.80); they are pooled for further analysis. Participants in the incentive groups lost significantly more weight than participants in the control group (Mean DC1&DC2=8.70 lbs, Mean Control participants = 1.17 lbs, t(64)=2.16, p=.035, 95% CI of the difference in means [.56, 14.50]). At 32 weeks, most incentive participants weighed less than they did at the start of the study (65.9% (29/44), 95% CI [50.1%, 79.5%]), whereas most participants in the control condition did not (45.5% (10/22), 95% CI [24.4%, 67.8%]) (χ2(1)=2.54, p=.11). Preliminary 9 month follow-up data suggest substantial amounts of weight regain such that the differences between the incentive groups and control group are no longer statistically significant (p=.56).
ConclusionsThe use of deposit contract incentives produced significant weight loss during this longer-term weight loss intervention, which appeared to be due to the duration of the intervention and not maintenance framing. However, due to substantial weight regain shown following the active phase of the intervention, future research should focus on habit formation and weight loss maintenance.
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