Official guidelines that urge people to follow a low-fat diet are having "disastrous health consequences" on the nation, a new report has warned.
"Eating a diet rich in full fat dairy - such as cheese, milk and yoghurt - can actually lower the chance of obesity," it adds.
"The most natural and nutritious foods available – meat, fish, eggs, dairy products, nuts, seeds, olive, avocados – all contain saturated fat. The continued demonisation of omnipresent natural fat drives people away from highly nourishing, wholesome and health promoting foods."
The authors of the report also argue that the science of food has been "corrupted by commercial influences".
But the report has been met by criticism from other scientists and Public Health England (PHE), who've said the suggestion we should be eating more fat is "irresponsible".
The new report also suggests that people with Type 2 diabetes should eat a fat-rich diet, rather than one based on carbohydrates, while the entire population should avoid sugar.
It advises people to stop counting calories and says the idea that exercise can help you "outrun a bad diet" is a myth.
The authors have questioned the advice in the government's official Eatwell Guide from PHE, claiming it was produced with a large number of people from the food and drink industry.
PHE reportedly worked with representatives from the British Retail Consortium, the Food and Drink Federation, and the Institute of Grocery Distribution, whose members include Tesco, Sainsbury's, Asda and Waitrose.
Professor David Haslam, chairman of the National Obesity Forum, told the Press Association: "As a clinician, treating patients all day every day, I quickly realised that guidelines...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, 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," he said.
"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 not everyone agrees with the latest report.
The British Dietetic Association has issued a statement to say it "does not support recommendations made by the National Obesity Forum in regards to reversing obesity and type 2 diabetes".
"This advice is potentially dangerous with possible adverse side effects," the statement says.
"Not only is there limited evidence around carbohydrate elimination for those with diabetes, but cutting out food groups could lead to nutrition problems including nutrient deficiencies and adversely affect their blood sugar control, particularly in individuals taking certain medications or insulin.
"With so much nutrition advice out there, it is unhelpful for the National Obesity Forum (NOF) to make such unsubstantiated claims.
"Whilst the NOF paper claims to be evidence-based, the evidence used is limited and the paper is not peer reviewed. It is simply adding to the confusion of the public and could potentially be damaging to public health."
Professor John Wass, the Royal College of Physicians' special adviser on obesity, added 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 (BHF), 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."
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