People need to avoid low-fat, processed foods and instead eat whole foods, such as meat, fish and dairy, says the National Obesity Forum and the Public Health Collaboration, a UK-based charity.

It’s sugars—and not fats—that are the real cause of obesity and heart disease, the charity says. Not only does eating fat not make us fat, full-fat foods such as milk, yoghurt and cheese can even protect the heart.

The current advice, which has been official policy since 1983, has resulted in people eating junk and processed foods and ‘bad’ carbohydrates, which are high in sugar.

Dr Aseem Malhotra, a cardiologist and member of the charity, said that the advice to eat a low-fat diet is “perhaps the biggest mistake in modern medical history, resulting in devastating consequences for public health.” The obesity epidemic is alone costing the UK’s National Health Service around £6bn a year.

The advice is based on flawed science but has also been influenced by the processed foods industry, which has funded research as well as individual scientists behind the advice over the years, he says.

Aside from eating fats and avoiding sugars and processed food, people should also be advised to avoid snacks between meals.