Lowering the Bar on the Low-Fat Diet

ByCrossFitDecember 20, 2019

In this 2016 editorial, Dr. David Ludwig outlines the breadth and implications of the U.S. government’s widespread calls to reduce fat intake beginning in the 1970s.

Ludwig describes the events as follows:

Beginning in the 1970s, the US government and major professional nutrition organizations recommended that individuals in the United States eat a low-fat/high-carbohydrate diet, launching arguably the largest public health experiment in history. Throughout the ensuing 40 years, the prevalence of obesity and diabetes increased several-fold, even as the proportion of fat in the US diet decreased by 25% … . A comprehensive examination of this massive public health failure has not been conducted. Consequently, significant harms persist, with the low-fat diet remaining entrenched in public consciousness and food policy.

Prior to these recommendations, over 40% of Americans’ energy intake came from fat, with whole milk and liberally fattened dishes and sauces commonplace. Also prior to these recommendations, evidence began to emerge suggesting the higher energy density of fat (nine calories per gram compared to four calories per gram for carbohydrate) alongside differences in the ways fat and carbohydrate metabolism are regulated made fat more obesogenic than carbohydrate. What followed was a rapid shift in public policy in which all Americans were encouraged to eat less fat and more carbohydrate, with even sugar presented as a suitable alternative to fat (1). These recommendations persisted in full force into the 1990s, when the Healthy People 2000 goals called on the food industry to increase the availability of processed low-fat foods (2). The food industry complied, replacing the fat in their foods with additional starches and sugars.

Since these recommendations, fat intake has fallen to near the recommended levels, while obesity has tripled and the incidence of a variety of metabolic diseases increased to an even greater extent. More recently, more rigorous trials have shown low-carbohydrate diets lead to greater weight loss, lower risk of weight gain, and improved metabolic health relative to low-fat diets (3). Meanwhile, publicly funded trials have failed to find benefits related to the use of low-fat diets (4).

Despite this evidence, much of the U.S. population continues to avoid fat as the failure of low-fat diets and relative success of low-carb diets have not been effectively communicated. Nutritional policy in schools continues to promote and subsidize low-fat, high-sugar foods (for example, banning whole milk while allowing sugar-sweetened nonfat milks). The link between sugar and heart disease is still viewed by many in the public health community as equivocal, despite the fact that much of the contrary evidence is now known to be the result of a concerted research effort funded by the sugar industry (5).

This situation persists, in part, due to a dearth of public funds dedicated to research of any diets other than the low-fat diet. Additional funding would allow for larger, more rigorous trials, which would be expected to further support the strong existing evidence supporting low-carbohydrate diets for health and weight loss.

Alternate dietary approaches deserve consideration, Ludwig argues, and the damage of the low-fat era must be undone.