The Effect of Small Wins on Body Fat Loss

This study, which spans 24 weeks (12 treatment, 12 post-treatment), aims to compare the effectiveness of 2 financial incentive structures: smaller rewards for achieving intermediate goals vs. a large reward for achieving an overall goal - on weight loss. Male Singaporeans or Permanent Residents between the ages of 25 and 60 will be recruited. Participants must be healthy and have a body mass index (BMI) of between 23 and 27.5, and own and use a smartphone or tablet. Participants will be given an individual-tailored percentage body fat (PBF) goal and will be blinded from the presence of different treatment conditions and randomly assigned to one of the three conditions for 12 weeks:

1. Control group. Participants will receive only participation fees.
2. One large reward treatment. Participants will be awarded S$X for reaching the PBF goal at the end of 12 weeks.
3. Small wins treatment. Participants in the Small wins treatment condition will also be given 3 triweekly intermediate goals (IGs). Specifically, given the PBF goal, the PBF Loss Target (LT) is the difference between the initial PBF measured at the first visit and the goal, i.e., LT = initial PBF - PBF goal. Then, the IG1 is to achieve 25% of the LT, the IG2 is to achieve 50% of the LT, and the IG3 is to achieve 75% of the LT. The cash rewards that participants will receive are capped by S$X and depend on which IGs participants achieve and whether participants maintain their progress at the end of the 12 weeks.

All participants will be given an individual-tailored 12-week percentage body fat (PBF) goal. The formula for this goal will be set in consultation with medical and fitness professionals (including certified doctors and fitness trainers) to ensure that it is safe, challenging, and achievable. The base formula, which assumes a 5% weight loss as is often defined to be the medically significant level, is:

(P* W - x*5%*W)/(95%*W)

where P is PBF at baseline (week 1), W is body mass in kg at baseline, P*W is their body fat mass at baseline, and x, ranging between 0% and 100%, is the parameter that is set in consultation with professionals. At 100%, it implies that all 5% in weight loss is from fat, vice versa.