Cutting back on butter, cream, cheese and other fatty foods is fuelling the obesity epidemic with disastrous consequences for health, experts have warned.
In a damning report that accuses major public health bodies in the UK of colluding with the food industry, the National Obesity Forum and the Public Health Collaboration said most of what we are told about healthy eating is wrong.
Calling for a "major overhaul" of dietary guidelines, it claimed that far from demonising fat, we should be eating more of it.
It also described sunflower oil as "barely a food", advised people to stop counting calories and warned that exercising does not help with weight loss.
The controversial claims have been criticised by other experts who accused the report's authors of cherry picking evidence to suit their own arguments.
But the report's authors say the epidemic's roots lie in the modern-day obsession with low-fat diets. The report cites studies which show a higher-fat, lower-carb diet to be superior.
It states: "Eating a diet rich in full-fat dairy - such as cheese, milk and yoghurt - can actually lower the chance of obesity.
"The most natural and nutritious foods available - meat, fish, eggs, dairy products, nuts, seeds, olives, avocados - all contain saturated fat."
The report also argued that the science of food has been "corrupted by commercial influences", with food industry representatives having a major influence on Public Health England's Eatwell Guide.
Co-author of the report, Aseem Malhotra, is a founding member of the Public Health Collaboration - a charity made up of dieticians, scientists and doctors.
He said promoting low-fat foods was "perhaps the biggest mistake in modern medical history resulting in devastating consequences for public health". The consultant cardiologist added: "Eat fat to get slim, don't fear it, fat is your friend. It's now truly time to bring back the fat."
But Professor Tom Sanders, of King's College London, said: "The claim that eating fat doesn't make you fat is absurd. If you eat a lot of fat, you will get fat."