Government and health charities have been doling out duff healthy eating advice for decades, but when are they going to admit it? That's the question raised by the remarks of cardiologist Aseem Malhotra, who writing in the BMJ has challenged the orthodoxy that the consumption of foods containing saturated fat, such as butter and red meat, causes heart disease.

Malhotra is brave and principled to speak out, yet he is far from a lone voice. In 2010, a major review of scientific studies on fat, published in the American Journal of Clinical Nutrition, concluded that contrary to what we have been lead to believe, "there is no convincing evidence that saturated fat causes heart disease". In the UK, other independent-minded nutritionists and medics, including John Briffa, Zoe Harcombe, and Malcolm Kendrick, have vociferously countered the biggest public health dogma of our times. It's the same story in the US, where influential voices, such as Garry Taubes, Michael Pollan and Robert Lustig, have all called time on the notion that saturated fat is the devil incarnate.

Why? Counter-intuitive though it might seem, there's no evidence that fat is fattening. Indeed by sating the appetite effectively, it may prevent overeating. To quote Kendrick, "there is not one molecule of evidence to suggest that saturated fat consumption causes obesity". What's certain is that saturated fat is a key component of our cell membranes, and essential for the production of certain hormones. It also acts as a carrier for important vitamins, and is vital for mineral absorption, and many other biological processes. So why has the public health establishment so assiduously encouraged us to shun it?

Viewed charitably, public health advice is just like any other socially constructed wisdom in that it gains authority through endless repetition. And who can blame GPs and other well-intentioned purveyors of health guidance up and down the land, if they recycle and disseminate uncritically tablets of nutritional wisdom dispensed from above?

Viewed cynically, however, it would be naive not to notice how the anti-sat-fat message has been used effectively by food manufacturers and processors to woo us away from whole, natural foods, such as butter, which is only minimally processed, on to their products, which are entirely the opposite, such as margarine.

For decades now, processed food companies have been using low-fat labels to give a halo of health to their industrially manufactured, nutritionally compromised, food constructions; everything from low-calorie yoghurt and pizza, to breakfast cereals and ready meals. The motto has been, if you want to sell crap, make sure it's low-fat crap, because few people will look beyond the low-fat label to scrutinise the product's composition.

The fatwa on sat fat has been a fabulous boon for the sugar and cereals industries. It acts as a red herring, drawing our attention away from the much likelier cause of obesity: an overabundance of sugar and refined carbohydrates, which disrupt blood sugar and insulin levels, encouraging fat production and storage in the body. It has been bad news for livestock farmers, who produce dairy and meat, but they don't have the lobbying might of the carb and sugar corporations.

But it's hard to admit that we got it wrong. Reacting to Malhotra's remarks, health charities have defended their low-fat advice in the usual kneejerk manner, despite it becoming increasingly obvious that it's time for a paradigm shift.

Consider the fate of eggs, one of nature's most complete foods. In the 1960s, the typical Briton ate five a week, then because they contained cholesterol, the nutritional establishment told us to eat no more than two. We dutifully acted on this guidance, and egg consumption slumped as we took in droves to eating nutritionally empty breakfast cereals. Three decades later, forced by unarguable evidence that eating cholesterol in eggs had no impact whatsoever on blood cholesterol levels, egg restriction advice was quietly ditched, and remodelled to say that eggs were part of a balanced diet.

Did we get an apology on eggs? Did we hell. So don't hold your breath waiting for a climb-down on saturated fat. The healthy eating establishment will choke on its low-fat cornflakes before it coughs that up.