Low-fat diets do not curb heart disease or help you live longer - the real enemy is sugar and carbohydrates, according to a leading scientist.
Current dietary advice is based on flawed evidence from the 1950s that has demonised saturated fat and put public health at risk, he said.
James DiNicolantonio, a cardiovascular research scientist in New York, said: 'We need a public health campaign as strong as the one we had in the 70s and 80s demonising saturated fats, to say that we got it wrong.'
Writing in the journal Open Heart, he added: 'There is no conclusive proof that a low-fat diet has any positive effects on health. Indeed, the literature indicates a general lack of any effect (good or bad) from a reduction in fat intake.
'The public fear that saturated fat raises cholesterol is completely unfounded.'
Experts believed the low-fat diet would lead to less obesity and diabetes - when the exact opposite was true, he added.
Evidence shows a low-carbohydrate diet - as opposed to a low-fat diet - actually improves cholesterol. However, he believed that processed foods should still be avoided.
British experts last year claimed that faulty interpretation of scientific studies had perpetuated a myth that a high-fat diet is bad for the heart. People were advised to reduce fat intake to 30 per cent of total energy and saturated fat intake to 10 per cent. However, research now fails to show a link between saturated fat intake and risk of cardiovascular disease, with saturated fat actually found to be protective.
Sweden has become the first western nation to develop dietary guidelines rejecting the low-fat myth, in favour of low-carb, high-fat nutrition advice.
Dr DiNicolantoni said: 'From these data, it is easy to comprehend that the global epidemic of atherosclerosis, heart disease, diabetes, obesity and the metabolic syndrome is being driven by a diet high in carbohydrate/sugar as opposed to fat, a revelation that we are just starting to accept.'
The best diet to boost and maintain heart health is one low in refined carbohydrates, sugars and processed foods, he said.
Brian Ratcliffe, professor of nutrition at Robert Gordon University, Aberdeen, agreed that the evidence failed to support advice to cut fat and saturated fat. 'Many who adhere to dietary dogma have chosen to ignore the uncomfortable facts that did not fit the hypothesis' he said.
But Professor Tom Sanders, head of diabetes and nutritional sciences division in the School of Medicine at King's College London, said Dr DiNicolantoni had misrepresented the scientific evidence.
'Refocusing dietary advice on sugar and away from fat modification and reduction is not helpful,' he said ( via dailymail.co.uk ).
Prof Sanders, who advises the industry-backed Global Dairy Platform, said: 'Dietary advice to avoid fatty meat products, choose reduced-fat dairy produce, and to restrict intakes of cakes, biscuits and puddings, which are often both high in saturated fat and sugar, and to select foods containing unsaturated oils such as nuts, fish and vegetable oils remain good sense. Those who fail to learn the lessons of history are likely to repeat its errors.'
Alison Tedstone, director of nutrition and diet at Public Health England, said: 'It is reasonable to conclude that a reduction in saturated fat intake will lower blood cholesterol, which may reduce the risk of developing heart disease.'