“They even sent you a codeword. You had to write it out on a piece of paper and include it in a photo with your foot and the scales, ” says Faith Archer, a fund blogger at website Much More With Less.
Faith is one of a number of UK dieters who have turned to weight loss “wager” websites as positive incentives.
Potential customers in the UK are now being targeted with adverts on social media.
David Roddenberry, co-founder of HealthyWage, told the BBC his firm started marketing to the UK this year.
The company stimulates personalised gambles with its customers, where they pick how much weight they would like to lose, and over what time. The prize money varies depending on the amount of weight a person has to lose.
Someone who wanted to lose a small amount of weight could bet PS3 00 in total over 10 months, but stimulate just PS33 if they succeeded. If they didn’t hit their objective, they would lose all of their money.
People who want to lose more win greater returns, assuming they achieve their stated goal.
“We’ve had about PS2 50,000 of contracts in the UK in the first month of the year, ” said Mr Roddenbury.
He added: “About one third of our participants achieve their goal and get a prize at the end.”
DietBet, the company that Faith signed up to, say that about 50% of clients win their four-week bets. It did not however provide data for those signing up to longer, more expensive bets.
“I am quite a competitive person and the idea I could actually make money by losing weight really appealed, ” says Faith.
“A friend of mine set up a DietBet group. Everybody who took portion put in $20( PS15. 46 ), because it’s a US company.
“The aim was to lose 4% of your body weight within four weeks and whoever managed to achieve that target would share out the money at the end.”
DietBet’s participants pool their money and the company takes a slice of that money. If everyone wins, it foregoes its share so that no one gets less back than they put in.
“We got sent vaguely promoting messages over the four weeks and there was a certain amount of chat among the group, ” says Faith.
“I had a bit of a panic at the end about whether I had actually done enough to win my wager. But actually, I lost a few pounds more than needed, ” she adds.
“Unfortunately, we must have been a really motivated group because it turned out everyone had won their bets.
“So I just got my $20 back. In fact, with the exchange rate I think I got slightly less back than I had put in at the beginning. But I had lost the weight and I think it did encourage me.”
On the surface, this looks like one route tech firms are trying to disrupt an existing market – weight loss is big business in the UK.
However, there are real concerns that because it is online and competitive, weight loss wagers could enable unhealthy and even dangerous behaviours.
A spokesperson for the British Dietetic Association( BDA) told the BBC: “The fact that they ‘gamify’ weight loss and add a competitive component to losing weight would be hugely detrimental to those with poor relationships with food.
“Those with eating disorders could use a website such as this to justify dieting and regulation for monetary gain. That could have significant impacts on both mental and physical health.”
The eating disorder charity Beat says it is very worried about the potential impact of these wager websites.
“The evidence is pretty clear that fitness wagers, fitness apps, anything where the individuals are able to track their weight loss and use that in a competitive or a ‘gamification’ way is extremely dangerous for people with eating disorder, ” said a spokesperson.