The recent revelation that the sugar industry tried to manipulate science in the 1960’s has led to a refocusing on the quality of scientific evidence in the field of nutrition as well as a re-look at ways to prevent diet-related chronic disease. In the early 1970’s the US government and major professional nutrition organizations recommended that people eat a low-fat/high-carbohydrate diet. Some argue that this launched the largest public health experiment in history. In the 40 some-odd years that have passed since those recommendations were made, the prevalence of obesity and diabetes increased several-fold, despite the fact that the average American diet contains 25 percent less fat. The 2015 USDA Dietary Guidelines for Americans, recognizing that the consumption of processed carbohydrates (white bread, white rice, chips, crackers, cookies, and sugary drinks) was driving the increase in both obesity and diabetes, basically eliminated the upper limit on dietary fat intake. But the low-fat diet remains locked in the public consciousness and therefore significant harms still persist. This massive public health failure of the 1960’s and 70’s remains to be comprehensibly examined.
In the mid-20th century US citizens consumed a higher-fat diet with more than 40 percent of calories coming from fat. At that time it was thought that processed carbohydrates caused weight gain. Back then virtually all milk was whole rather than low-fat and fats were used liberally in cooking, sauces, and salad dressings. But in a few decades this all changed as small studies suggested the benefits of a low-fat diet. Fat is a high-density energy food with 9 calories per gram as opposed to 4 calories per gram for carbohydrates and proteins. In addition, high fat foods are tasty and cause less satiety, or the feeling of being full, as compared to carbohydrates. So the experts said that “it was difficult, if not virtually impossible, to overeat on a high-carbohydrate diet”. So by the late 20th century the government switched to recommending a low-fat, high-carbohydrate diet.
Recent research suggests that the focus on reducing dietary fat has led to an increase in chronic disease. Research also shows that low-carbohydrate and low-glycemic (sugar) diets lead to a reduction in insulin levels and long-term weight-loss maintenance. Some experts argue, however, that the low-fat dietary recommendations were meant to increase consumption of vegetables, fruits, and whole grains, not increase carbohydrate and sugar consumption. They maintain that it was the sugar industry that hijacked the low-fat diet and twisted it into something that was unintended. We may never know the whole truth.
So current dietary recommendations focus on low-carbohydrate, low-sugar diets with increases in the use of fruits, vegetables, whole grains, and nuts and seeds. Recommendations on protein consumption remain the same while focus on fat intake has lessened significantly. All this naturally includes the assumption that one makes reasonable dietary choices. Just because the focus on fat intake is reduced doesn’t mean a daily ice cream sundae is now ok.