Food labels displaying the amount of exercise needed to burn off calories could have a triggering effect for those vulnerable to eating disorders, campaigners warn.
Research by Loughborough University found putting exercise targets on food could help people consume less.
But campaigners said the move could be “triggering” to those living with mental health conditions.
One charity urged policymakers to consider the impact of the labelling.
Using data across 14 studies, researchers found labelling exercise calories could cut about 200 calories from a person’s average intake.
The study revealed it takes about four hours to walk off the calories in a pizza, or 22 minutes to run off a chocolate bar.
But Tom Quinn, from eating disorder charity Beat, said: “Although we recognise the importance of reducing obesity, labelling food in this way risks being incredibly triggering for those suffering from or vulnerable to eating disorders.
“We know that many people with eating disorders struggle with excessive exercising, so being told exactly how much exercise it would take to burn off particular foods risks exacerbating their symptoms.
“Policy makers looking to incorporate this change need to consider the impact that it may have on people’s mental health.”
Tally Rye, a personal trainer and health influencer, said the idea of explicitly linking exercise with calories on food packaging would “promote feelings of shame and guilt around food”.
“I don’t think it will lead to long-term positive changes to having a healthy lifestyle,” she said.
“Regardless of whether we have a completely sedentary day, we still need calories.
“This is also quite ableist – it is cutting out those who may not find it easy to move. Are the elderly not allowed to eat if they can’t do the vigorous exercise required?”
“A more positive way to look would be to think how food can fuel a workout,” she added.
Campaigner Hope Virgo said that, despite being in recovery from an eating disorder for 11 years, she fears the sight of exercise calorie information on food packs could impact her.
“Even though I am 11 years into my recovery I know that if I walked into a shop and saw that information I would find that incredibly triggering,” she said.
“There isn’t one thing that causes an eating disorder, but this idea adds to it and adds to the pressure. It will trigger people to feel certain things and in itself that is just as risky.”
Another person who has lived with an eating disorder, Rich, told BBC Radio 5 Live’s Your Call programme that he found the idea of an exercise calorie label “frightening”.
“I think anybody who has gone through an eating disorder, to then hear this kind of information that you’re putting out this morning it is frightening,” he said.
Rich recalled linking his calorie counts with exercise at the beginning of his eating disorder.
He added: “Food is an absolute necessity and it should be enjoyed not something you are looking at and worrying about. I think it is a very dangerous game.”
Prof Amanda Daley, who led the research at Loughborough, told the BBC “there is no evidence that physical activity campaigns lead to eating disorders”.
“We are not disregarding people with eating disorders, but this is about educating the broader public,” she said.
“If you ask the public, they say that current food labelling is confusing. We have all different types of labels. Our view is that we need to put all the information in as clear a way as possible.
“When you say how much exercise is needed to burn off a muffin it is really clear.”
The Department for Health declined to comment due to the upcoming general election.
For information and support on eating disorders, visit the BBC’s Action Line.