title: DietBet: A Web-Based Program that Uses Social Gaming and Financial Incentives to Promote Weight Loss.
abstract: BACKGROUND
  Web-based commercial weight loss programs are increasing in popularity. Despite their significant public health potential, there is limited research on the effectiveness of such programs.
  
  
  OBJECTIVE
  The objective of our study was to examine weight losses produced by DietBet and explore whether baseline and engagement variables predict weight outcomes.
  
  
  METHODS
  DietBet is a social gaming website that uses financial incentives and social influence to promote weight loss. Players bet money and join a game. All players have 4 weeks to lose 4% of their initial body weight. At enrollment, players can choose to share their participation on Facebook. During the game, players interact with one another and report their weight loss on the DietBet platform. At week 4, all players within each game who lose at least 4% of initial body weight are declared winners and split the pool of money bet at the start of the game. Official weigh-in procedures are used to verify weights at the start of the game and at the end.
  
  
  RESULTS
  From December 2012 to July 2013, 39,387 players (84.04% female, 33,101/39,387; mean weight 87.8kg, SD 22.6kg) competed in 1934 games. The average amount bet was US $27 (SD US $22). A total of 65.63% (25,849/39,387) provided a verified weight at the end of the 4-week competition. The average intention-to-treat weight loss was 2.6% (SD 2.3%). Winners (n=17,171) won an average of US $59 (SD US $35) and lost 4.9% (SD 1.0%) of initial body weight, with 30.68% (5268/17,171) losing 5% or more of their initial weight. Betting more money at game entry, sharing on Facebook, completing more weigh-ins, and having more social interactions during the game predicted greater weight loss and greater likelihood of winning (Ps<.001). In addition, weight loss clustered within games (P<.001), suggesting that players influenced each others' weight outcomes.
  
  
  CONCLUSIONS
  DietBet, a social gaming website, reached nearly 40,000 individuals in just 7 months and produced excellent 4-week weight loss results. Given its reach and potential public health impact, future research may consider examining whether a longer program promotes additional weight loss.
authors: Brown Medical School, Department of Psychiatry and Human Behavior, The Miriam Hospital's Weight Control and Diabetes Research Center, Providence, RI, United States. tleahey@lifespan.org.
authors: Tricia
authors: T
authors: Leahey
authors: Jamie
authors: J
authors: Rosen
keywords: Web-based intervention; commercial weight loss; financial incentives; social gaming