Money may not buy happiness, but it might give low-income obese people an extra incentive to lose weight, a new study suggests.
The study, of people from urban neighborhoods, found that cash rewards encouraged participants to shed some extra pounds, versus a weight-loss program with no financial bonuses.
And the effects were similar whether people were rewarded for reaching their weight-loss goals, or simply for making healthy lifestyle changes.
Over six months, 39% to 49% of people given cash incentives lost at least 5% of their starting weight. That compared with 22% of study participants given no monetary motivation.
The caveat, experts said, is that no one knows how financial rewards pan out in the long run. In this study, the weight-loss differences among the groups had begun to narrow by the one-year point.
"This would only be impactful if people could keep losing weight at this rate over the longer term," said Karen Glanz, of the University of Pennsylvania's Center for Health Incentives and Behavioral Economics in Philadelphia.
Glanz, who was not involved in the study, said that researchers still have much to learn about the role for financial incentives in weight loss -- including how and when it's best to use them.
The concept itself is not new.
Studies have suggested that offering people money in exchange for lost pounds can bear fruit -- at least in the short term. Those findings have inspired web-based programs, like DietBet and HealthyWage, which use the prospect of financial rewards to encourage people to shed weight.
The reasoning behind the approach stems from the simple fact that weight loss is hard.
Obesity is a medical condition, not just a matter of willpower, said senior researcher Dr. Melanie Jay, an associate professor at NYU Langone Health in New York City.
To lose weight and keep it off, Jay said, people have to battle biology -- as the body tries to hang onto fat, not lose it. They are also fighting their daily environment, full of high-calorie processed foods and often little chance for physical activity.
For low-income people -- who cannot readily join a gym or afford healthy foods -- the obstacles are particularly daunting, Jay said.
Financial incentives are seen as a potential way to give people immediate rewards for the hard work of trying to lose weight.
But like Glanz, Jay said there are many unknowns.
"What makes financial incentives work," she asked, "and what are the best ways to use them?"
For their study, Jay's team tested two kinds of incentives: One rewarded people for outcomes -- losing at least 5% of their starting weight, which, on average, meant about 10 pounds. The other rewarded people's efforts, like getting regular exercise.
In both cases, participants could earn up to $750 over six months.
The study, published Dec. 5 in the journal JAMA Internal Medicine, involved 668 adults from low-income neighborhoods in New York City and Los Angeles. The majority were Hispanic.
The participants were randomly assigned to three groups. In all three, people received a voucher for a free year at Weight Watchers, a digital scale and a fitness tracker. Everyone was told to attend at least two Weight Watchers meetings a month, weigh themselves at least three times a week, work up to 150 minutes of exercise per week, and keep track of their diets using a food diary.
People in the financial incentives groups were rewarded either for meeting those goals, or for losing 5% of their starting weight.
In the end, neither incentives tactic was the clear winner, Jay said. At the six-month mark, people rewarded for weight loss were doing somewhat better, but by one year -- after the financial rewards ended -- the difference between the two groups had vanished.
Around 41% in both groups had managed to keep 5% of their starting weight off. Meanwhile, the group with no cash incentives had slowly improved: about 31% had lost 5% of their initial weight, compared with 22% at the six-month mark.
To Glanz, that leaves the question of whether any short-term benefits from cash incentives will last. Plus, she said, the average weight loss in all three groups was modest -- at about 6 to 11 pounds.
So the even bigger question is whether financial incentives ultimately improve people's health, Glanz said. To get someone to pay the incentives -- employers, health plans or society -- studies will probably have to show health benefits.
Jay agreed that evidence on the "cost-effectiveness" of financial incentives is needed.
She also noted that because obesity is so tough, lifestyle changes alone may just not be enough for many people.
The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has advice on managing obesity.
SOURCES: Melanie Jay, MD, associate professor, department of medicine, and department of population health, NYU Langone Health, New York City; Karen Glanz, PhD, MPH, professor, University of Pennsylvania Perelman School of Medicine, affiliated faculty, Center for Health Incentives and Behavioral Economics, University of Pennsylvania, Philadelphia; JAMA Internal Medicine, Dec. 5, 2022, online