The British government has criticised a report that suggested people should not be afraid of eating fat as MPs warned it had prompted "public outcry and confusion".
The National Obesity Forum and the Public Health Collaboration called in the report for a "major overhaul" of current dietary guidelines, saying encouraging people to stick to low-fat diets is harming their health.
But the report was condemned by health minister Alistair Burt who agreed with Public Health England's assessment that it was "irresponsible".
The report suggests that a focus on low-fat diets is failing to address Britain's obesity crisis.
It advocates a return to eating "whole foods" like meat, fish and dairy as well as high fat healthy foods like avocados.
It also argues that saturated fat does not cause heart disease while full fat dairy - including milk, yoghurt and cheese - can actually protect the heart.
The report suggests that foods labelled as "low fat" and "low cholesterol" should be avoided and it has prompted a backlash within the scientific community.
The report was raised in the House of Commons as an urgent question by Labour MP Keith Vaz.
The chairman of the Commons home affairs select committee said: "The National Obesity Forum's report published today has led to a public outcry and confusion.
"Indeed the conclusions of this report contradict much of the health and lifestyle advice issued by the government and the NHS over the last decade.
"Ordinary people are now caught in a whirlwind of conflicting advice at a time when they desperately need clarity, consistency and straight talk.
"Quite simply they don't know where to turn."
Mr Burt said that international health organisations agree that "too much saturated fat raises cholesterol" and increases the risk of heart disease and obesity.
He said: "I am pleased that you have provided the opportunity for us to agree with you and others that have said that this report is irresponsible."
Experts disagree on causes of obesity
Professor David Haslam, chairman of the National Obesity Forum, said: "As a clinician, treating patients all day every day, I quickly realised that guidelines from on-high, suggesting high carbohydrate, low fat diets were the universal panacea, were deeply flawed.
"Current efforts have failed - the proof being that obesity levels are higher than they have ever been, and show no chance of reducing despite the best efforts of government and scientists."
Dr Aseem Malhotra, consultant cardiologist and founding member of the Public Health Collaboration, a group of medics, said dietary guidelines promoting low fat foods "is perhaps the biggest mistake in modern medical history resulting in devastating consequences for public health.
"Sadly this unhelpful advice continues to be perpetuated. The current Eatwell guide from Public Health England is in my view more like a metabolic timebomb than a dietary pattern conducive for good health. We must urgently change the message to the public to reverse obesity and Type 2 diabetes.
"Eat fat to get slim, don't fear fat, fat is your friend. It's now truly time to bring back the fat."
Professor Iain Broom, from Robert Gordon University in Aberdeen, said: "The continuation of a food policy recommending high carbohydrate, low fat, low calorie intakes as 'healthy eating' is fatally flawed.
"Our populations for almost 40 years, have been subjected to an uncontrolled global experiment that has gone drastically wrong."
But Professor John Wass, the Royal College of Physicians' special adviser on obesity, said there was "good evidence that saturated fat increases cholesterol".
He added: "What is needed is a balanced diet, regular physical activity and a normal healthy weight. To quote selective studies risks misleading the public."
Professor Simon Capewell, from the Faculty of Public Health, said: "We fully support Public Health England's new guidance on a healthy diet. Their advice reflects evidence-based science that we can all trust. It was not influenced by industry.
"By contrast, the report from the National Obesity Forum is not peer reviewed. Furthermore, it does not it indicate who wrote it or how is was funded. That is worrying."
Dr Mike Knapton, associate medical director at the British Heart Foundation, said: "This report is full of ideas and opinion, however it does not offer the robust and comprehensive review of evidence that would be required for the BHF, as the UK's largest heart research charity, to take it seriously.
"This country's obesity epidemic is not caused by poor dietary guidelines; it is that we are not meeting them."
Dr Alison Tedstone, chief nutritionist at PHE, said: "In the face of all the evidence, calling for people to eat more fat, cut out carbs and ignore calories is irresponsible.
"Unlike this opinion piece, our independent experts review all the available evidence - often thousands of scientific papers - run full-scale consultations and go to great lengths to ensure no bias."
Professor Naveed Sattar, from the University of Glasgow, said the report's "main headline - simply to eat more fat - is highly contentious and could have adverse public health consequences".