Kathleen Louden

November 03, 2015

CHICAGO — Weight-loss contracts might be more effective when financial consequences are attached, new research indicates.

In fact, weight loss was greatest when an online goal-setting platform required that people who missed their goals donate money to a charity against their beliefs and values, said lead investigator Lenard Lesser, MD, from the Palo Alto Medical Foundation Research Institute in California.

Previous research has shown "that paying people to lose weight is less effective than them losing their own money," he explained. "People are averse to loss."

This could account for the increase in websites in recent years that offer nonbinding commitment contracts to help people change health behaviors.

"This type of tool is probably good for people who know how to lose weight but are having trouble sticking with it," Dr Lesser told Medscape Medical News.

He presented the results here at the American Public Health Association 2015 Annual Meeting.

Sticking to the Plan

Dr Lesser and his colleagues analyzed data from 3857 such weight-loss commitment contracts entered into by repeat users of the free StickK program. The company did not provide funding for the study, and did not provide information about participants' height, income, or race, according to Dr Lesser.

Participants input their weight, height, target weight, and date of desired goal completion, and the program calculates the average number of pounds they need to lose each week. They can then choose to have self-selected payments deducted from a credit card if they do not achieve their weekly goal, and can direct that money to go to a friend, a general charity fund, or a charity they do not agree with.

Weight verification was not required, but participants could have a friend monitor their progress or could step on a wireless scale to automatically upload their weight to the site, said Dr Lesser.

For a missed weight-loss goal, 1008 participants directed deductions to an unappealing charity, 436 directed deductions to a general charity, and 407 directed deductions to a friend.

The 2006 participants who set up no deductions were slightly younger than those who set up deductions (< .001), and were more likely to be female (< .001).

Most contracts lasted 14 to 17 weeks, but some lasted almost 100 weeks. Participants risked about $8 to $10 per week, according to a press release.

Your Money or Your Health

On regression analyses that controlled for participant age, sex, and the presence of a previous commitment contract, weekly weight loss was significantly greater in the three deduction groups than in the no-deduction group (< .001).

Table. Percentage of Weight Loss per Week

Deduction Weekly Weight Loss, %
Unappealing charity 0.33
General charity 0.28
Friend 0.25
None reference


For the 1079 participants whose weight loss was verified, the difference in weight loss remained significant between the unappealing charity group and the no-deduction group (< .001). In addition, participants who directed deductions to a friend lost 0.36% more weight than those who did not.

However, reports of weight loss might have been biased, and the lack of randomization is a study limitation, Dr Lesser acknowledged. "Maybe people who put down deposits were more motivated to lose weight."

It is also not clear whether the participants who lost more weight ate healthier. The website provides no information about how to lose weight or eat healthy, he told Medscape Medical News.

But "we know the participants lost weight, which is a surrogate outcome for becoming healthier," he explained.

Because this is a secondary data analysis, this is just "a first step," said Marsha Spence, PhD, MPH, RDN, from the Department of Nutrition at the University of Tennessee in Knoxville, who was not involved with the study.

However, "it's intriguing that giving money to an 'anticharity' helped participants lose more weight. It should spark interest in doing more research on this topic," she told Medscape Medical News.

Dr Spence said she thinks electronic and mobile health tools are the way of the future for public health professionals and healthcare providers. "To reduce obesity rates, we're going to need these novel approaches," she said.

Dr Lesser and Dr Spence have disclosed no relevant financial relationships.

American Public Health Association (APHA) 2015 Annual Meeting: Abstract 330448. Presented November 2, 2015.


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