The low-fat-diet regimen is turning out to be based on bad science, but the USDA has been slow to catch on.
By Nina Teicholz
Oct. 28, 2014 6:56 p.m. ET
“The top scientist guiding the U.S. government’s nutrition recommendations made an admission last month that would surprise most Americans. Low-fat diets, Alice Lichtenstein said, are “probably not a good idea.” It was a rare public acknowledgment conceding the failure of the basic principle behind 35 years of official American nutrition advice.
Yet the experts now designing the next set of dietary recommendations remain mired in the same anti-fat bias and soft science that brought us the low-fat diet in the first place. This is causing them to ignore a large body of rigorous scientific evidence that represents our best hope in fighting the epidemics of obesity, diabetes and heart disease.
The Dietary Guidelines for Americans—jointly published by the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services (HHS) every five years—have had a profound influence on the foods Americans produce and consume. Since 1980, they have urged us to cut back on fat, especially the saturated kind found mainly in animal foods such as red meat, butter and cheese. Instead, Americans were told that 60% of their calories should come from carbohydrate-rich foods like pasta, bread, fruit and potatoes. And on the whole, we have dutifully complied.
By the turn of the millennium, however, clinical trials funded by the National Institutes of Health (NIH) were showing that a low-fat regime neither improved our health nor slimmed our waistlines. Consequently, in 2000 the Dietary Guidelines committee started to tiptoe away from the low-fat diet, and by 2010 its members had backed off any mention of limits on total fat.
Yet most Americans are still actively trying to avoid fat, according to a recent Gallup poll. They are not aware of the USDA’s crucial about-face because the agency hasn’t publicized the changes. Perhaps it did not want to be held responsible for the consequences of a quarter-century of misguided advice, especially since many experts now believe the increase in carbohydrates that authorities recommended has contributed to our obesity and diabetes epidemics.
Such a humbling reversal should have led the expert committee preparing the 2015 Dietary Guidelines, which holds its next-to-last public meeting Nov. 6-7, to fundamentally rethink the anti-fat dogma. But instead it has focused its anti-fat ire exclusively on saturated fats. Recent guidelines have steadily ratcheted down the allowable amount of these fats in the diet to 7% of calories “or less,” which is the lowest level the government has ever advised—and one that has rarely, if ever, been documented in healthy human populations.
The most current and rigorous science on saturated fat is moving in the opposite direction from the USDA committee. A landmark meta-analysis of all the available evidence, conducted this year by scientists at Cambridge and Harvard, among others, and published in the Annals of Internal Medicine, concluded that saturated fats could not, after all, be said to cause heart disease. While saturated fats moderately raise “bad” LDL-cholesterol, this does not apparently lead to adverse health outcomes such as heart attacks and death. Another meta-analysis, published in the respected American Journal of Clinical Nutrition in 2010, came to the same conclusion. The USDA committee has ignored these findings.
No doubt, accepting them would be another embarrassing reversal for nutrition experts. The USDA, the NIH and the American Heart Association have spent billions trying to prove and promote the idea that saturated fats cause heart disease.
In place of saturated fats, these agencies have counseled Americans to consume ever-larger quantities of unsaturated fats, which are found mainly in soybean and other vegetable oils. Yet a diet high in these oils has been found in clinical trials to lead to worrisome health effects, including higher rates of cancer. And the USDA, which espouses a commitment to finding healthy “dietary patterns” based in history, is now in the paradoxical position of telling Americans to derive most of their fats from these highly processed vegetable oils with virtually no record of consumption in the human diet before 1900.
The most hopeful path lies in a different direction: An enormous trove of research over the past decade has shown that a low-carbohydrate regime consistently outperforms any other diet in improving health. Diabetics, for instance, can most effectively stabilize their blood glucose on a low-carb diet; heart-disease victims are able to raise their “good” HDL cholesterol while lowering their triglycerides. And at least two-dozen well-controlled diet trials, involving thousands of subjects, have shown that limiting carbohydrates leads to greater weight loss than does cutting fat.
The USDA committee’s mandate is to “review the scientific and medical knowledge current at the time.” But despite nine full days of meetings this year, it has yet to meaningfully reckon with any of these studies—which arguably constitute the most promising body of scientific literature on diet and disease in 50 years. Instead, the committee is focusing on new reasons to condemn red meat, such as how its production damages the environment. However, this is a separate scientific question that is outside the USDA’s mandate on health.
Rates of obesity in the U.S. started climbing dramatically right around 1980, the very year in which the Dietary Guidelines were first introduced. More than three decades later, more of the same advice can only be expected to produce similarly dismal health outcomes. And the cost, in human and dollar terms, will continue to be catastrophic.
These are compelling reasons for Congress to ask the USDA and HHS to reconstitute the Dietary Guidelines committee so that its members represent the full range of expert opinion. The committee should then be mandated to fundamentally reassess the Guidelines’ basic assumptions, based on the best and most current science. These measures would give millions of Americans a fighting chance in their battle against obesity, diabetes and heart disease—and at last start to reverse the ill effects of our misguided Dietary Guidelines.”