Dietbet: Saviour or Scammer?

A stranger approaches you at a bar. He wants to bet $140 that he can lose 4 kilograms (8.8 pounds) in 4 weeks. If he loses the weight you pay him odds of 50 to 1 (that’s $7000); if he doesn’t you keep his money. Doesn’t sound very attractive, right? The funny thing is that four out of five times, according to this research, you’d win the bet.

Why does this matter? Well, with a bunch of online diet betting services like Dietbet, GymPact, and HealthyWage growing in prominence I thought I’d explore the effectiveness of financial incentives for motivating weight loss. Are they an innovative tool that will help defuse the developed world’s fat bomb, or are they a cunning ruse? Let’s take a look.


A quick glance at the Dietbet and HealthyWage websites and you’ll find research that supports gambling as a viable weight loss technique. Although HealthyWage cites a couple of studies, it was Diebet’s efforts that were the most impressive.

In collaboration with Assistant Professor at Brown Medical School, and Dietbet Advisor, Tricia Leahey, Dietbet’s CEO Jamie Rosen co-authored this journal article examining the effectiveness of Dietbet’s gambles on weight loss. Using Dietbet’s flagship wager – a bet to lose 4% of your bodyweight in 4 weeks – the study looked at data from 1,934 bets that involved 39,387 users. Unlike the study mentioned in my intro, Dietbet wagers were far more successful. Almost 44% of gamblers — compared to 20% in the abovementioned study – won their bets with an average win of US$58.79. Of the people that did win, almost one third achieved a clinically significant weight loss. These findings are pretty impressive. Unfortunately, one positive result doesn’t cut it in the scientific world so let’s dig deeper.


Individual studies examining financial incentives for weight loss are contradictory and messy. A good way to cut through this mess is to look at meta-analyses, which combine results from multiple studies to identify reoccurring trends. The most comprehensive meta-analysis I’m aware of – and that only included experiments using the gold standard experimental design – found that financial incentives, when compared against behavioural weight loss treatments, had “no significant effect… … on weight loss or maintenance at 12 months and 18 months”. Because long-term maintenance is essential for realising the health benefits of weight loss our confidence in HealthyWage, Dietbet and others should be dented.

Although gambles and incentives don’t seem to be that effective in the long-term, it’s hard to argue that they don’t work for short term weight loss. Financial incentives shouldn’t be the only treatment for obesity, but it seems logical that they be integrated somewhere in this treatment. Research has shown, for example, that financial rewards for changing a bad habit lead to more weight loss than directly rewarding weight loss itself. But before we rush to include financial incentives in our weight loss routine, there’s something else we need to be mindful of.


A famous meta-analysis (referenced in Dan Pink’s excellent TED Talk on the counterintuitive effects of incentives) showed that financial incentives mess with our motivation. When we’re given money to do something our extrinsic motivation is increased at the expense of our intrinsic motivation. This means if jogging gives you a sense of achievement but you start getting paid to jog, this enjoyment will be reduced. The research also suggests that you won’t start enjoying it again once the payments stop. The money, in other words, spoils your fun. There is evidence that similar things happen when incentives are applied to weight loss. Indeed, this study found that once incentives for weight loss stopped, weight regain was faster for people who were paid to lose weight – seemingly because they had no motivation to maintain their exercise and dietary changes.


Conclusive statements about the effectiveness of financial incentives for motivating weight loss are difficult due to a number of unanswered questions in the research. However, because long-term weight loss and maintenance is essential for realising the health benefits of weight loss, the lack of lasting weight loss when financial incentives are involved is a concern. Also of concern is the possibility that such incentives, when removed, could reduce our intrinsic motivation to engage in healthy behaviours that protect us from weight gain. But hey, if it works for you, go for it.

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