How deposits and lotteries increased short-term weight loss by 10 pounds

Incentives: Anything that motivates someone to do something, such as salespeople earning additional money based on what the quantity that they sell, or “working on commission.”

Loss Aversion: A cognitive bias that describes why the loss felt from money, or any other valuable object, can feel worse than gaining the same thing.

Regret Aversion: This occurs when a decision is made to avoid regretting an alternative decision in the future, people sometimes make decisions in order to avoid this outcome.

Previous attempts to promote weight loss

An effective treatment for obesity is a significant clinical challenge – it’s difficult to achieve weight loss at a relatively cost-effective level, especially weight loss that lasts for more than 12 months. Behavioral interventions and pharmacotherapy are costly and tend to produce follow-up weight loss of only 3 to 5 kilograms. An alternative, surgical treatment, comes with incredibly high costs and high complication rates, though it is effective in inducing weight loss for larger individuals.

Why incentives need to be in the home

Many advantageous effects of behavioral economics have not been tested in combination with incentive studies in the past. Some incentive-based approaches in the past have applied incentives to physicians rather than participants – these approaches may not have the desired effect, as health care delivery deficiency only accounts to 10% of premature mortality, in contrast to unhealthy behaviors (smoking, poor diet, or sedentary lifestyles) that account for 40% of premature mortality in the US.

Theoretical background

To improve on past studies and current literature, this study aimed to combine the advantageous effects of behavioral economics and financial incentives. Researchers incorporate the CrI2SP behavior change framework and designed the intervention with three key research findings in mind:

1. Small rewards and punishments can create a great incentive effect if they occur immediately.
2. Individuals are motivated by past rewards and the prospect of future rewards, in addition to being especially attracted to the small probability of large rewards.
3. The desire to avoid regret is very powerful in decision making under risk.

Who did they study?

In this study, eligible participants fell between the ages of 30-70 and had a Body Mass Index (BMI) of 30-40. The effects of the incentives were tested against a control group in a Randomized Controlled Trial (RCT). The weight-monitoring program lasted 16 weeks, involving monthly weigh-ins. Participants were randomized into three groups: two intervention groups and one control group. The two intervention groups received the following incentives:

1. Deposit contract: participants were allowed to contribute between $0.01 and $3 per day for a month, with a refund occurring if they had met or exceeded the weight loss goal. As an incentive for participants to contribute, the study matched the participant’s contribution in addition to a $3 daily fixed payment. Participants were aware that each day that they called in and reported a weight at or below their goal, they would accumulate rewards and receive an almost instant text message letting them know how much they had earned that day. 
2. Lottery contract: participants in the lottery who reported a weight at or below their goal were eligible for a daily lottery prize with an expected value of $3 per day. This lottery was designed to provide infrequent large payoffs, a 1% chance of a $100 reward, and frequent small payoffs, a 20% chance of a $10 reward. Again, participants received almost instant daily feedback via text message about their daily payoff.

Nonadherent participants in both incentive groups also received rapid text message feedback on what their payoff would have been, had they met their weight goal. Participants who lost 20 lb or more during the 16 week study also received a bonus of $50.

To reduce the chance of participant dropout at the end of the month for participants whose weight was higher than their goal, they were given a fresh start at the start of the month. This adjusted the slope of the weight trajectory whilst keeping the overall weight loss goal the same. Follow-up weigh-ins were conducted 7 months after the start of the study. 

A 10-pound difference

After 16 weeks, both incentive groups produced a mean weight loss greater than the control group. The deposit contract group had a mean weight loss of 14 lb and the lottery contract group lost a mean of 13.1 lb. In contrast, the control group only lost a mean of 3.9 lb.

There were qualitatively similar patterns regardless of the participant’s age, income or BMI at the start of the study. Furthermore, 36.8% of participants in the deposit contract group lost at least 20 lb, compared to 26.3% in the lottery group and 5.3% in the control group.

Limitations

However, it is also important to note that participants in both incentive groups gained weight between the completion of the incentive intervention and the 7 month follow-up. Though the net weight loss at the start of the study and after 7 months was greater in the incentive groups, at 6.2 lb for the deposit contract group and 9.2 lb for the lottery contract, than in the control group, 4.4 lb.

While weight loss can increase health and longevity, there were no effective long-term results, suggesting the intervention does not have long-term positive impacts on its participants

The study was fairly homogenous and does not provide insight on other groups’ responses to financial weight loss incentives

Participants were required to pass eligibility criteria in order to participate, to ensure their safety

Can Money Buy Good Health? – RCT of Financial Incentives for Weight Loss: This perspective by The Decision Lab outlines how people are particularly attracted to tangible and immediate incentives, and how studies have used this knowledge to introduce effective financial incentives for weight loss.

The Stages of Change: How to Motivate, Facilitate, and Reinforce Desired Behaviors: Changing habits isn’t exactly straightforward. The Decision Lab explores the difficulty and conscious effort required to break down learned behavioral patterns to change our habits, in addition to the challenges associated with learning a new behavior.

How Loss Aversion Affects Our Perceptions of Weight: Loss aversion demonstrates how we register losses more acutely than we do gains, and that we tend to make decisions in the interest of avoiding potential losses. This perspective by The Decision Lab explores the role loss aversion plays in weight gain.