This study demonstrates the effectiveness of incentive systems based on behavioral economics in promoting weight loss. Lost to follow-up rates were much lower than is typical in weight loss studies, suggesting that this approach was successful in keeping participants engaged, and significant weight loss was achieved without coupling the incentive program with an intensive, expensive weight loss program. Weight loss of the magnitudes obtained in the incentive conditions has been shown to improve immediate outcomes such as blood pressure, glycemic control, and serum lipid levels, and a mean weight loss of 5.5 kg has been associated with a reduction in the incidence of diabetes of 58% over an average follow-up interval of 2.8 years.7, 8
However, substantial amounts of weight were regained between the end of the weight loss phase and the follow-up 3 months later. This suggests that to achieve long-term weight loss such programs need to run for a longer period of time, and the optimal duration of such programs is an important question for further investigation.
Our work expands understanding of how financial incentives can contribute to weight loss. In a recent study, Finkelstein and colleagues found that over a 3 month period participants offered $14 per percentage point of weight loss lost 4.7 pounds and participants offered $7 per percentage point of weight loss lost 3.0 pounds compared to 2.0 pounds among control group participants.10
Jeffrey and colleagues had earlier demonstrated that significant weight loss could be achieved using deposit contracts,11, 12
but these studies had required substantial up front payments and the incentive programs were tied to intensive weight loss programs. The large up front payments (equivalent to about $800 in today’s dollars) led to about 15% of potential participants responding to invitations to join the Jeffrey study in contrast with 81.4% in this study. Incentive-based approaches that involve applying incentives to participants rather than providers have great potential to change participant health behaviors.6, 13-16
This is important because unhealthy behaviors such as smoking, poor diet, and sedentary lifestyles may account for as much as 40% of premature mortality in the United States, whereas deficiencies in health care delivery may account for only 10% of premature mortality.17
The interventions in this study were designed to take advantage of several effects identified in the behavioral economics literature. First, consistent with research showing that even small rewards and punishments can have great incentive value if they occur immediately,18-21
participants received rapid feedback about whether they won and non-adherent participants received feedback about whether they would have won had they been adherent. Second, based on research showing that people are motivated by the experience of past rewards and the prospect of future rewards,22
and that people are particularly emotionally attracted to small probabilities of large rewards,23
the lottery provided frequent small payoffs (a 1 in 5 chance at a $10 reward) and infrequent large payoffs (a 1 in 100 chance at a $100 reward). Third, research on decision making has found that the desire to avoid regret is a potent force in decision making under risk,24
so by giving participants who did not lose weight feedback about what they would have won had they been adherent, the incentive scheme maximized the anticipated threat of regret by people who fail to adhere. Anticipated regret has been shown to affect a variety of preventive behaviors, such as the significant increase in vaccination use among people who experienced illness after failing to get vaccinated.25
Lotteries also provide variable reinforcement, an approach known to be especially effective in reinforcing behavior.26
The use of deposit contracts is a powerful mechanism for inducing behavior change that is based on ”loss aversion,” a psychological concept first described by Nobel Prize winner Daniel Kahneman and Amos Tversky in 1979. Loss aversion has been used to explain many inconsistencies in traditional economic choice models, including anomalous patterns of choice under conditions of uncertainty.27,28
Critical to using loss aversion to motivate behavior is the concept of decision isolation; people react so powerfully to small losses and gains in part because they consider them in isolation and fail to integrate them psychologically with the often much larger fluctuations in income arising from work-earnings and investments.29,30
An important outstanding question is the sustainability of weight loss achieved through incentives, as maintenance of successful weight loss has been a big challenge.31, 32
Our results clearly indicate that incentive programs must be focused on both attainment of initial weight loss and maintenance of weight loss. The need for effective weight management strategies has taken on increasing urgency because of markedly increasing rates of obesity.2, 33, 34
Many behavioral interventions and pharmacotherapy are costly and generally produce only modest (3 to 5 kg) weight loss.35
Surgical treatment, while effective in inducing weight loss in morbidly obese participants, has a relatively high rate of complications and high costs.36
While the study was limited to veterans at a single facility, we have no reason to think that the participants were different than those at other facilities in terms of likely responsiveness to the intervention, though follow-up studies should examine the relative responsiveness to incentives of men and women in different health care settings.
In conclusion, incentive approaches based on behavioral economic concepts appear to be highly effective in inducing initial weight loss. These approaches could be highly effective in modifying a wide range of difficult to change health behaviors. Further work is needed to test the effectiveness and cost effectiveness of these approaches in achieving sustained weight loss.