In the past decade, the National Institutes of Health finally began funding randomized-control trials of carbohydrate-restricted diets, as has the Dr. Robert C. Atkins Foundation, but these trials have been designed to test only the hypothesis that such diets can be used safely and effectively as a means to lose weight. The subjects are overweight and obese, and the studies compare weight loss and heart-disease risk factors with the results of low-fat or calorie-restricted diets. These trials are neither planned nor interpreted as tests of the hypothesis that it is the carbohydrates in the diet—“the sugar and starchy elements of food,” as The Lancet phrased it 140 years ago—that cause fattening and obesity to begin with. Rather, the underlying assumption here, too, is that weight loss is caused inevitably by negative caloric balance—consuming fewer calories then we expend—and the investigators perceive these trials as testing whether carbohydrate restriction allows us to do so with more or less facility than semi-starvation diets that reduce calories directly or reduce fat calories specifically.

A direct test of the carbohydrate hypothesis asks the opposite question: not whether the absence of refined and easily digestible carbohydrates and sugars causes weight loss and is safe, but whether the presence of these carbohydrates causes weight gain and chronic disease. Such a trial would ideally be done with lean, healthy individuals, or with a spectrum of subjects from lean through obese, including those with metabolic syndrome and Type 2 diabetes. They would be randomized into two groups, one of which would consume the sugary and starchy elements of food and one of which would not, and then we would see what happens. We might randomly assign a few thousand individuals to eat the typical American diet of today—including its 140–50 pounds of sugar and high-fructose corn syrup a year, nearly 200 pounds of flour and grain, 130-plus pounds of potatoes, and 27 pounds of corn—and we could assign an equal number to eat a diet of mostly animal products (meat, fish, fowl, eggs, cheese) and leafy green vegetables. Since the latter diet would be relatively high in fat and saturated fat and calorically dense, the conventional wisdom is that it would cause heart disease and, perhaps, obesity and diabetes. So this would test the dietary-fat/cholesterol hypothesis of heart disease, as well as the carbohydrate hypothesis.