The effect of pair-based monetary contingency contracts for weight loss: Results from a randomized controlled pilot study

Abstract

Objective: Monetary contingency contracts (MCCs), in which deposited money is returned contingent on weight loss, could promote weight/adiposity reduction. This study piloted individual- and pair-based MCCs (when refunds are contingent on two individuals losing weight) and assessed effects on weight/body composition. Methods: Seventy-seven participants with BMI greater than 25 kg/m2 were recruited. In a non-blinded, randomized controlled trial conducted in a university laboratory setting, participants were randomized in pairs via a computer-generated sequence to one of four conditions: partner with pair-based refund (P-PBR), partner with individual refund (P-IR), individual weight loss with individual refund (I-IR), or no MCC (comparison). Refunds were contingent on weight loss after 4 and 8 weeks; weight/body composition was measured at 0, 4, and 8 weeks. Primary outcome measures were change in weight and fat mass. Results: Seventy-seven participants (P-PBR n = 16; P-IR n = 20; I-IR n = 22; comparison n = 19) were recruited. Deposit amount was significantly positively associated with reductions in weight/BMI. At 8 weeks, the P-PBR condition reduced fat mass more than all other conditions (P < 0.05) and reduced weight/BMI more than the I-IR condition (P < 0.05). Conclusions: The large effect of P-PBR on fat mass suggests it would be valuable to conduct a fully powered, randomized controlled trial of pair-based MCCs.