Expert casts doubt over the value of low-fat diet

Diets low in saturated fat do not prevent heart disease or improve health and, instead, public health warnings need to be issued over sugar, a leading scientist has said.

The fear that saturated fat raises cholesterol is “completely unfounded,” while the current recommendations to follow a low-fat diet are based on flawed evidence, he added.

Writing in the journal Open Heart, leading US cardiovascular research scientist Dr James DiNicolantonio said a “compelling argument can be made for the general lack of evidence in support of a low-fat diet”.

Advising people to replace saturated fat with carbohydrates or omega 6 polyunsaturated fats was not supported by scientific research.

“A change in these recommendations is drastically needed, as public health could be at risk,” he said, adding that the rise in diabetes and obesity over recent years correlated with the increase in carbohydrate consumption “not saturated fat”.

He went on: “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 as the low-density lipoprotein particle size distribution is worsened when fat is replaced with carbohydrate.”

Instead, he said the culprits of increasing poor health are diets high in carbohydrate and sugar and a public health campaign is “drastically needed to educate on the harms of a diet high in (these foods)”.

Dr DiNicolantonio said the idea that fat causes heart disease was based on a flawed 1950s study which used data from six countries, but excluded data from another 16. This study “seemingly led us down the wrong ‘dietary road’ for decades”.

The initial Dietary Goals For Americans, published in 1977, proposed increasing carbohydrates and decreasing saturated fat and cholesterol in the diet.

Dr DiNicolantonio said: “This stemmed from the belief that since saturated fats increase total cholesterol [a flawed theory to begin with] they must increase the risk of heart disease.”

Experts also believed the diet would lead to less obesity and diabetes, when the exact opposite was true, he added. Furthermore, evidence shows that a low-carbohydrate diet (as opposed to a low-fat diet) actually improves cholesterol.

“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,” Dr DiNicolantonio said.

Brian Ratcliffe, professor of nutrition at Robert Gordon University, Aberdeen, welcomed the article.

“DiNicolantonio does not even touch on the evidence which shows that low-fat diets have been associated with poor mood and even depression.”

He said it was too “simplistic” to blame carbohydrates and sugar for rising obesity in the US.