Diet apps are peddling plans for slimmers that may cause deadly weight loss.
A spate of mobile phone apps, offering plans as low as 700 calories a day, have advertised on TV as firms bid to cash in on the new year fitness boom.
But a Sunday People investigation found some schemes fail to screen participants for a history of eating disorders and allow dangerously low weight-loss targets to be set.
Some even let pregnant women sign up.
One leading app, Noom, which costs £44 a year, allowed a 5ft 10in woman to set a weight-loss goal of 6st 7lb, giving her a BMI of 13.
A BMI of between 18.5 and 24.9 is considered ideal for most adults and anything below 15 could indicate a potentially fatal case of anorexia.
FatSecret said this could be done by sticking to a diet of just 700 calories a day – on top of a rigorous exercise regime.
SparkPeople allowed a goal of a BMI of 17, along with a calorie budget of 1,000.
Our probe comes just weeks after an NHS study found one in five women in England may have an eating disorder.
Healthy adults typically need between 2,000 and 2,500 calories a day.
Andrew Radford, chief executive of eating disorder charity Beat, said: “By allowing people to set very low weight-loss targets and failing to screen users for disordered eating, these weight-loss apps pose a serious risk to the health of people with eating disorders and could lead to devastating consequences.
“Strategies to reduce obesity are important for the health of the population.
"However, they need to be carefully considered to ensure they do no harm to people with eating disorders.
“Beat is calling for eating disorder experts to be involved in the design of campaigns and products, screening to prevent people at risk of eating disorders from signing up, and language of shaming people living with obesity to be avoided.
“The constant narrative around weight loss and ‘improvement’ can often feel overwhelming for people affected by eating disorders.
“We would encourage anyone struggling to report harmful content wherever possible, but also consider taking a step away and instead focusing on other positive sources of support like Beat’s website and helpline.”
Data from NHS Digital last month showed 19% of women asked about their relationship with food screened positive for an eating disorder.
Shockingly, in women under 35 the figure was 28%. In men, the figure was 13% or one in eight.
Beat previously hit out at TV doctor Michael Mosley for his Fast 800 diet – featured on Channel 4 documentary Lose a Stone in 21 Days.
It said calls to its helpline rocketed while the program was on air.
Dr. Mosley overhauled the £100 plan after it was discovered that it let users set potentially fatal targets.
He also changed meal plans which would mean users surviving on fewer than 700 calories while also following an exercise program.
Dr. Joanna Silver, lead eating disorder therapist at London's Nightingale mental health hospital, said: "A BMI of 13 is potentially fatal and you might need to be hospitalized.
"You'd be in a terrible shape and you wouldn't be able to function. "You'd be in danger of heart failure, especially if you lost the weight very quickly.
"It's likely you'd develop osteoporosis which is not reversible. It's extremely likely if you're a woman that your periods would stop."
She added: “You would not be able to focus or put any mental energy into work because we also need calories to burn in our cognitive efforts as well.”
Lose It! said that the company had updated its app after we had completed our probe and users were now warned if their daily calorie budgets put them at risk.
"The Lose It! app was recently updated to warn users of potentially harmful daily calorie budgets and in early 2021 is also planning to implement these same warnings across the other areas of the app where users are setting a weight goal.
“Lose It! also actively seeks to support its members with expert content that encourages a positive relationship with food through its blog, on which both members and non-members can access content from registered dietitians on many topics, including warning signs of disordered eating.