HOW To Lose A Stone In 21 Days has been branded "dangerous" after contestants showed off their six stone weight loss.
Channel 4's latest diet show - hosted by Michael Mosley - has caused controversy with viewers who claim it's "triggering huge eating disorders".
But the presenter insists: "People say that rapid weight loss is dangerous, but it's not if its healthy eating."
Encouraging a low calorie and high protein fuelled diet, the programme documents dieters looking to make huge lifestyle changes.
Last night it was revealed five volunteers lost a combined six stone in three weeks after their final weigh-in on an 800 calorie a day diet.
Some viewers were upset about the show, with one tweeting: "I genuinely cannot believe this show.
"Of course you’ll lose a stone in 21 days if you’re doing a double whammy of 800 cals a day (starvation diet) & keto.
"You’ll also put it straight back on again with an eating disorder into the bargain. I’m raging #howtoloseastonein21days."
Another added: "Mosleys ‘fast 800’ program talks about developing a healthy relationship with food, but then his show goes on to demonise eating a single raisin?
"Anorexia can lead to loss of brain matter - no amount of ‘mindfulness excercises’ will be enough to fix that #howtoloseastonein21days."
Someone else said: "I’ve done something similar to this a few weeks before a wedding. It worked in terms of looking slimmer. The weight stayed off for a good 7 months.
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"But mentally this could be disastrous for anyone who could be tempted to continue eating this way long term #howtoloseastonein21days."
Another viewer disagreed, arguing: "@DrMichaelMosley just watched #howtoloseastonein21days. Fantastic watch. I've also read your books. I hugely admire the way you educate people on their diets.
"I'm following a low FODMAP diet but still struggle with intolerances. Any plans to do a programme about that?"