BWHealthy Weight Pilot Study: A randomized controlled trial to improve weight-loss maintenance using deposit contracts in the workplace.

Objective: Deposit contracts, where participants "bet" on achieving a goal and get their money back only if successful, have been shown to be effective for short-term weight-loss. This pilot study examined their effect on weight-loss maintenance.

Methods: From 2016 to 2018, we conducted a pilot, 50-week randomized controlled trial among 42 hospital employees (19 intervention and 23 control), in Boston, Massachusetts, who lost ≥10 lb (4.5 kg) in the two years prior to enrollment. Participants were recruited primarily in-person. Both control and intervention participants were asked to attend a weigh in weekly and received weekly email communication. Intervention participants also entered into a deposit contract to maintain baseline weight within ≤2 lb (0.9 kg). We examined weight change from baseline to 50 weeks (primary outcome) and maintenance of baseline weight at 50 weeks (secondary outcome; binary - yes v. no). Participants completed baseline and follow-up surveys and received incentives for completion.

Results: At baseline, mean (SD) weight was 83.2 (15.5 kg) among intervention and 80.7 (14.5 kg) among control participants. After 50 weeks, intervention participants had slightly less but non-significant weight gain (adjusted β -1.12 kg; 95% CI -5.28, 3.05) than control participants; 73.7% of intervention v. 39.1% of control participants met their weight-loss maintenance goal by study end (adjusted OR 4.78; 95% CI 1.01, 22.71).

Conclusions: A deposit contract was not associated with differences in weight but led to more participants meeting their weight-loss maintenance goals; a deposit contract for weight-loss maintenance should be tested in a full-scale intervention. Most intervention participants viewed the deposit contract as acceptable.