This is the first study to demonstrate that deposit contract incentives can successfully help keep weight off for 32 weeks, a result that appeared to be due to the duration of the intervention and not maintenance framing.
However, substantial weight was regained following cessation of the incentives and health and economic benefits require sustained weight loss. For this reason, devising techniques to promote weight loss maintenance following cessation of financial incentives is an important topic for future research. Success in improving health and economic outcomes through sustained weight loss may require augmenting this intervention with a more effective approach to habit formation.
This study contributes to evidence of the effectiveness of incentive systems based on behavioral economics in promoting weight loss. The intervention was designed to take advantage of several effects identified by behavioral economics, including over-optimism12,13
and loss aversion.14
People tend to be over-optimistic in predicting their weight loss; therefore, when asked to put money down at the beginning of the month toward losing weight, most participants did so. Then, after having made a deposit, loss aversion was used to motivate weight loss, as participants did not want to lose the money they had deposited. Finally, consistent with research showing that even small rewards and punishments can have great incentive value if they occur immediately,15–18
participants received rapid feedback.
Interestingly, at 16 weeks our results were qualitatively similar to those of Volpp et al.7
Mean weight loss in the incentive conditions was 10.3 pounds (95% CI, 7.1–13.5), compared to 13.1 (95% CI, 2.0–16.4) and 14.0 (95% CI, 3.7–16.4) pounds in the incentive arms in the study by Volpp et al.7
Similarly, in the present study, 34.1% (95% CI, 20.5%–49.9%) of incentive participants attained the 16-week weight loss goal; in Volpp et al.'s study,7
goal attainment rates in the incentive arms were 47.4% (95% CI, 24.5%–71.1%) and 52.6% (95% CI, 28.9%–75.6%).
In this previous study, deposit contracts were supplemented with a $3 direct payment per day, which was not included in the present study.7
Based on net incentive earnings and mean weight loss, the average cost per pound of weight loss was $10.14 in the present study—much less than that of the deposit contract ($27.04) and lottery incentive ($20.82) arms of the Volpp et al.'s study.7
That most participants made a deposit each month, even though they usually did not attain their weight loss goal, is perhaps indicative of the pervasiveness of over-optimism.19
Failing to attain weight loss goals month after month did not deter people from making subsequent deposit contract contributions. This point attests to the utility in using decision errors to help people to attain their goals.
Although incentive participants lost more weight than controls, most did not attain their monthly weight loss goals. Not only were the goals ambitious, they became progressively more challenging because, as a proportion of total body mass, they increased over time, as participants lost weight. Future research could investigate the effectiveness of tapering goals off over time or of allowing participants to set their own goals.
That there was no effect of maintenance framing on weight loss could mean that framing does not matter, but it could also mean that the manipulation was too subtle. And, while maintenance framing may not affect weight loss, it may affect other important outcomes, such as attrition. For example, consistent with the goal-setting literature, breaking a weight loss program into different sub-components may make attaining overall weight loss goals seem less daunting, resulting in lower attrition rates.20
This conjecture is consistent with the current study: while four people withdrew from the condition in which the program was not broken into phases (DC2), only one person withdrew when such distinctions were made (DC1) (P
= 0.035). Lost to follow-up rates were lower than is typical in weight loss studies, suggesting that this approach keeps participants engaged.
The primary limitations of this study, discussed in that of Volpp et al.,7
are: external validity (participants were predominantly male veterans motivated to lose weight); inability to determine the impact of feedback, independent from incentives, on weight loss; and the study staff could not be blinded due to the nature of the intervention.
In summary, this article indicates that incentive approaches based on behavioral economics are effective in inducing weight loss over an 8-month intervention period. Future research is needed to devise techniques that promote sustained weight loss over longer periods of time.