Eating disorder charities have issued a warning about a "harmful" diet app that had been promoted on the Apple App Store to over-12s.
Carrot Fit aims "to transform your flabby carcass into a Grade A specimen of the human race" using encouragement in the form of light-hearted abuse.
It said it had helped thousands of users meet their health goals.
But critics said that the app was irresponsible and could trigger eating disorders.
Since the concerns were brought to its attention, Apple has raised the age recommendation on the app's page to over-17s.
"The way they are addressing weight is inappropriate and scary. It's not a healthy body image and it's irresponsible," said Gemma Oaten, manager of eating disorder charity Seed. She called for the app to be banned.
"These apps, and the platforms they are put on, have a duty of care - especially during a pandemic when eating disorders have skyrocketed.
"We are fighting to save lives. This just undermines it all."
Carrot Fit was featured by Apple as part of a short list of recommended fitness apps which appeared at the top of the App Store. It is not available on Android's Play Store.
"Tap for a much-needed motivation boost," the list read.
Phrases including "meatbag", "lay off the ice-cream or else" and being granted "permission to watch your friend eat a bag of potato chips", were identified as terms that might be particularly problematic for those with eating disorders.
"The content and language could be very triggering for an individual with an eating disorder and in my professional opinion should be restricted or banned," psychologist and eating disorder specialist, Dr Khanya Price-Evans, said.
"It is criminal that this industry is preying on the vulnerability of young people and creating a body dissatisfaction with an archaic oppressive approach."
The app currently has a rating of 4.6 out of five.
Positive reviews say it is "entertaining" and "makes working out less daunting".
"The funny comments from Carrot turn exercising and fitness into a positive experience for users, rather than a negative one," developer Brain Mueller explained. "The safety and wellbeing of Carrot Fit's users is my primary concern and I have included a number of safety warnings inside the app.
"The app does state that if users lose weight too fast, the carrot character will get angry - suggesting that the developers have, to at least some degree, considered some of the risks," said Dr Dawn Branley-Bell, health and cyber-psychologist at Northumbria University. "But this may not be sufficient to limit the negative psychological impact, particularly in relation to the language used in the app."
There were also concerns that the app was promoting weight loss to children because it was labelled in the App Store as being suitable for ages 12 and above.
Mr Mueller said this was a "mistake" and that the app's terms and conditions explicitly stated that Carrot Fit was not intended for use by anyone under the age of 18. He told the BBC that Apple had been asked to update its page.
Hope Virgo, a mental health campaigner who developed anorexia when she was 13, said this sent a dangerous message.
"Because it's still being advertised to 12-year-olds, children will download it without any scrutiny," she said. "They haven't finished developing, and demonising 'fatness' at this point is appalling to see."
Apple has not responded to requests for comment from BBC News.
"I've been struggling with my eating disorder for 10 years and this language for me is not encouraging - it proves that diet culture is still being worshipped.
"Typically among eating disorders the illness lists foods that are 'good' and 'bad' and we cut these foods completely out of our diet, so for an app to suggest that ice-cream is bad is very triggering and could be very detrimental for someone with an eating disorder.
"Eating disorders have some of the highest mortality rates in mental illnesses... I'll let that sink in.
"Yes this completely should be banned. I can see how people would say it is "light-hearted" and "a joke" but these people are ignorant to something that is very serious."
"I could never touch an app like that. But maybe, just maybe, there's some guy out there who finds motivation in that kind of language, and for him that technology will drive him to a better place.
"If it hurts me but helps them, how do app developers navigate it?
"For me personally, it's absolutely fine if health and wellness is tied to a goal. I have goals and I think they're great. But I think it's important we hold those goals alongside the knowledge that even if we DON'T achieve them, we are not 'failures' or some 'flabby carcass'.
"We are just humans, doing our best and working towards things that make us feel healthier, or stronger, or whatever we want to feel."