One of the toughest parts about losing weight is keeping it off for the long-term. This is partly because, compared to our previous diet, the brain thinks we're in a period of starvation, so it battles back against the weight loss—driving up hunger. There are various ways to make the lost pounds stay lost, but a recent study published in the journal Social Science and Medicine showed that cash rewards can work well to extend the duration of weight loss.

For the study, the researchers set up an eight-month study that first had 161 subjects pay $168 to join a 16-week weight-loss program in which they were counseled weekly on how to sustain a healthy lifestyle. They also paid $119 to join a rewards program that gave them cash back or a lottery ticket which set them up with a 1-in-10 chance of netting 10 times the cash if they met their goals. Other rewards for hitting 5% or 8% at months four and eight were also offered. In all, they stood to get a maximum of $475 if they met all of the requirements.

By the fourth month of the experiment, those in the rewards group had lost more than twice the weight of the control group; at the eighth and 12th months, weight loss was still higher for those enrolled in the cash cohort. Also, about 40% of the rewards group lost 5% or more of their weight at month four, compared to 12% for the control; and at month 12 the cash group was at 28%, while the control barely reached 17%.

Cash paid out to the rewards participants ended up being $162, which left them with about a cost of $43 for the program—about 42% of subjects ended up with a profit. Though most lost money, they also lost weight and were happy to play the game, with around 80% saying they approved of the rewards arrangement.

"Even small amounts of weight loss, sustained over time, confer great health benefits and can help prevent chronic disease. This study shows that the enhancement and maintenance of weight loss is feasible through a rewards program with participant ownership, coupled with an evidence-based, medical weight-loss program," said study co-author Kwang Wei Tham, M.D., senior consultant in the department of endocrinology at the Singapore General Hospital.