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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.
The objective of our study was to examine weight losses produced by DietBet and explore whether baseline and engagement variables predict weight outcomes.
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.
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 (
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.
Over 45% of the world population and approximately 66% of American adults are overweight or obese [
In contrast, commercially available weight loss programs have wide reach, particularly Web-based interventions. In fact, a large percentage of individuals who attempt weight loss report using commercial programs [
Despite their potential to improve public health, the scientific literature on the effectiveness of Web-based commercial weight loss programs is sparse [
This study examined the effectiveness of DietBet, which is a commercially available Web-based program that uses social gaming and financial incentives to promote weight loss. Upon enrollment, players join a game and enter money into a pool. All players have 4 weeks to lose 4% of their initial body weight. During the game, players report their weight and interact on the DietBet platform. At the end of the game, all players within each game who lose at least 4% in 4 weeks are declared “winners” and split the initial pool of money bet at enrollment. The primary aim of this study was to conduct a naturalistic examination of engagement, retention, and weight loss outcomes in DietBet. Previous findings from financial incentive weight loss trials have shown that the possibility of losing large (vs small) amounts of money for not meeting weight goals motivates better overall weight loss [
DietBet is a social gaming website that uses financial incentives and social influence to promote weight loss. Players are recruited via press coverage (eg, Today Show, CNN, New York Times, Wall Street Journal), business development efforts (popular wellness experts with social capital are asked to host games and encourage fans/followers to participate), direct virality (players recruit other players), and indirect virality (players share DietBet information on Facebook). At enrollment, players bet money and join a game. Players are given the option to join an existing game that has not yet started or create their own game. If they create their own game, it can be either open (anyone can join) or closed (invite only; ie, all players know each other).
Players are prompted to submit their official start weight two days prior to the start of the game, (see below for weigh-in procedures). Once the game begins, players have 28 days to lose 4% of their initial body weight. DietBet does not promote a specific diet or weight loss strategy; instead, players are allowed to choose any strategy to lose weight (eg, low-fat diets, low-carbohydrate diets, etc). During the game, players post photos, comments, and weight loss tips (
Intervention screenshot.
DietBet keeps a portion of the initial pool of money to cover financial transaction costs and staff time associated with weight verification, customer service, and tech support. DietBet’s share is taken out of each game’s starting pool of money before winners are paid. Thus, players who do not win do not incur a charge to play. DietBet retains 15%-25% of the payout depending on the amount of each individual bet (US $1-$99–25% fee; US $100-$249–20% fee; US $250 or more–15% fee).
Participants report their gender at the beginning of the game. Within 48 hours prior to the start of each game, participants are required to complete an official weigh-in. Similarly, within 48 hours after the end of a game, participants are to complete an official weigh-in. Official weigh-in procedures involve the submission of two photos, one of the player on a scale in light indoor clothing without shoes and another that captures the scale’s readout and a piece of paper that includes the player’s weigh-in password. DietBet staff reviews each photograph for player-password correspondence. In addition, DietBet uses prespecified algorithms to detect any unusual weight outcomes and game activity; specifically, across games DietBet will identify players who have won more than US $300 in DietBets and identify players who have unusual weight gain between DietBet games (ie, gained more than 1% per day). Those individuals are flagged and DietBet staff completes a detailed review of their weight, game activity, and profile information. Using these algorithms and the photo-based system within 48 hours of the start and end of a game, if a weight is deemed questionable, players are required to submit extra proof by completing a live Skype weigh-in with one of DietBet's referees, a video weigh-in, or an in-person weigh-in at a DietBet approved location (eg, Walgreens drugstores or Customer Value and Service drugstores).
All weigh-in, social engagement, and Facebook data were obtained directly from the DietBet website. Specifically, during the game, players reported their weight on the DietBet platform and weigh-ins were summed for each player. Players interacted with one another by cheering, posting pictures, posting status updates, “liking” others’ posts, and commenting on and replying to posts; to create an overall social engagement variable, the number of social interactions for each variable (cheers, pictures, updates, etc) were summed for each player. DietBet collected data on whether players posted their game participation on Facebook; data were coded 1 for “Yes” or 0 for “No.” The option to share on Facebook was not available in early games. Thus, the sample size for this variable is smaller than the overall sample (n=20,059 vs N=39,387).
The amount of money bet and the amount of money won was obtained objectively via payment transaction data.
The number of players on each game and whether all players knew each other (closed game/invite only vs open game) were obtained objectively by extracting data from the platform.
Player characteristics, engagement, and completion outcomes were examined using simple descriptive statistics, including means, standard deviations, and percentages. Completers (ie, those who completed an official weigh-in procedure at the end of the game) and noncompleters were compared using analyses of variance or chi-square tests for continuous or categorical variables, respectively. To examine the effects of DietBet on weight loss, a conservative baseline carried forward intention-to-treat approach was used; players who did not finish the game (ie, did not complete a final, verified weigh-in) were assumed to have remained at baseline/entry weight and within subjects
The Miriam Hospital’s Institutional review board approved this study.
From December 2012 to July 2013, 39,387 players participated in 1934 games on the DietBet platform. Players were predominantly female (84.04%, 33,101/39,387) with a mean baseline weight of 87.8kg (SD 22.6kg). The average amount of money bet at game entry was US $26.84 (SD US $21.93). Upon enrolling, 50.03% of players chose to share their DietBet participation on Facebook (note–the option to share on Facebook was not available in earlier games, thus the total sample size for this variable was n=20,059, of those n=10,036 shared their DietBet participation). During the 4-week game, players completed an average of 5.3 (SD 3.9) weigh-ins and engaged in 9.3 (SD 78.4) social interactions (eg, cheers, posts, likes, etc).
A total of 71.71% of participants (28,244/39,387) self-reported their weight into the DietBet platform during week 4, and 65.63% (25,849/39,387) completed an official weigh-in at the end of the game (ie, completed the photo-based weigh-in process immediately following the game). A greater proportion of men completed a photo-verified weigh-in than women (Men–68.39%, 4292 out of 6275; Women–65.10%, 21,550 out of 33,101;
Intention-to-treat analyses (assuming that individuals who did not complete an official, photo-based weigh-in at the end of the game did not lose any weight) showed that players lost a significant amount of weight from baseline to the end of the game (
Player weight loss.
|
Total sample |
All winners |
Winners who lost ≥ 4% |
Winners who lost most weight in game |
% weight loss, mean (SD) | 2.6 (2.3) | 4.9 (1.0) | 4.9 (0.9) | 3.4 (0.9) |
Participant baseline characteristics and game variables predicted weight loss outcomes and whether a player won their game. Significant predictors of greater percent weight loss were male gender (
Winners’ versus nonwinners’ baseline characteristics and engagement.a
|
Winners |
Nonwinners |
Winners versus nonwinners |
Male, n (%) | 3489 (20.32) | 803 (9.25) | <.001 |
Baseline weight kg, mean (SD) | 87.1 (22.1) | 88.1 (22.4) | <.001 |
Amount bet US $, mean (SD) | $29.79 ($29.18) | $23.83 ($12.30) | <.001 |
Shared on Facebook,b
|
4837 (53.19) | 2241 (46.79) | <.001 |
Weigh-ins, mean (SD) | 7.0 (4.2) | 5.4 (3.1) | <.001 |
Social engagement, c
|
13.6 (113.6) | 8.8 (38.4) | <.001 |
aGiven that completion was associated with baseline characteristics and engagement, to control for potential confounding of completion, only game completers were included in these analyses, n=25,849.
bOption to share on Facebook was not available in early games. Thus, the sample size for this variable is smaller than the overall sample of completers. Specifically, of those who were given the option to share on Facebook, n=20,059, a total of n=13,882 completed the game. Of those, n=9093 were winners and n=4789 were nonwinners.
cSum of cheers, comments, replies, likes, photos, and updates.
In a multivariate model, all variables remained significant, independent predictors of weight loss (
The 39,387 players represented a total of 1934 games. Weight loss tended to cluster within games (
DietBet, a 4-week commercial Web-based program for weight loss, yields retention results that are comparable to other programs [
DietBet results compare favorably to other Web-based commercial programs and to more intensive programs. In reports of the Biggest Loser Club, participants self-reported their weight loss less than once a week [
The favorable outcomes produced by DietBet may be attributed to its social gaming components-namely, the use of financial incentives and social influence. Results showed that those who bet more money and had greater social engagement had a greater magnitude of weight loss and were more likely to “win” their game. These findings are consistent with those from behavioral economics and with findings in the behavioral weight loss literature. Behavioral economics suggests that loss aversion (the strong tendency to avoid losing something that is owned) is a significant motivator of human behavior and that the magnitude of loss may moderate the effect, with greater potential loss yielding greater motivation [
Players who reported their weight loss more often also lost more weight. Not only is regular reporting indicative of better program engagement, which alone is associated with better outcomes [
In addition to examining individual effects, we also explored the effects of game characteristics on outcomes. Consistent with previous findings showing that weight loss clusters in team-based weight loss competitions [
Study limitations include a predominantly female sample, lack of some player characteristic data (age, race, ethnicity, etc), the short program length, and lack of fully objective weight data. Majority female participation is common in weight loss trials and commercial weight loss programs [
This study has several strengths. It provides a reliable and ecologically valid examination of the true engagement, retention, and weight loss achieved in DietBet, a wide-reaching, commercial, Web-based weight loss program that uses financial incentives and social influence to promote weight loss in large numbers of individuals. Only a small number of studies have conducted a naturalistic examination of such programs. Moreover, these previous studies have obtained only self-report weight [
Intervention screenshot of player progress.
intraclass correlation coefficient
The authors would like to acknowledge all DietBet staff and players who made this report possible.
Mr Rosen is the chief executive officer of DietBet, Inc and receives salary support from the company.