title: The effect of pair-based monetary contingency contracts for weight loss: Results from a randomized controlled pilot study.
abstract: 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.
  
  
  
  Seventy-seven participants with BMI greater than 25 kg/m2were 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.
  
  
  
  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).
  
  
  
  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.
authors.affiliation: School of Psychology, University of Leeds, Leeds, UK.
authors.forename: Bianca J
authors.initials: BJ
authors.lastname: Sykes-Muskett
authors.affiliation: School of Psychology, University of Leeds, Leeds, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Prestwich
authors.affiliation: School of Psychology, University of Leeds, Leeds, UK.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Lawton
authors.affiliation: Manchester Centre for Health Psychology, Division of Psychology and Mental Health, School of Health Sciences, University of Manchester, Manchester, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Armitage
mesh_terms: D050154:Adiposity / Q000502:physiology*; D000328:Adult; D001521:Behavior Therapy; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000523:psychology / Q000628:therapy*; D010865:Pilot Projects; D016896:Treatment Outcome; D015431:Weight Loss