Good Calories, Bad Calories

The argument that carbohydrate-restricted diets work by the same mechanism as calorie-restricted diets only changes the nature of the dilemma we have to unravel. It does not make it disappear. Even if we accept Yudkin’s notion that all people who lose weight while abstaining from carbohydrates do so because they spontaneously feel the compulsion to eat less, we must then explain why anyone would willingly suffer the symptoms of semi-starvation—hunger, irritability, depression, and lethargy—rather than simply eat another piece of cheese, or steak, or lamb. The standard explanations are that it’s simply too much trouble to do so, or that “all-you-can-eat-diet[s],” as Jane Brody wrote in the New York Times in 1981, “so restrict the dieter’s choices that boredom and distaste automatically produce a calorie cutback.” But these are unacceptably facile. If the obese end up eating less on this diet, the most likely explanation is that they’re less hungry, in the same way that, if we don’t drink water when water is there for the drinking, we’re probably not thirsty. If we don’t feel or act semi-starved, it’s a reasonable bet that we’re not. “The best definition of food deficiency,” as Ancel Keys and his colleagues wrote in The Biology of Human Starvation, “is to be found in the consequence of it.”

Keys’s starvation studies suggest where the “no bread, no butter” logic will take us. We know from these studies that if we feed people a carbohydrate-rich diet of fifteen or sixteen hundred calories a day, they will be obsessed with the “persistent clamor of hunger,” so much so that they might be willing to mutilate themselves to escape the ordeal. Meanwhile, if those same people were allowed to consume unlimited calories of only meat, cheese, and eggs, this school of thought dictates, they will voluntarily restrict their consumption to the same fifteen or sixteen hundred calories—or at least they will if they’re obese or need to lose ten or twenty pounds—because in this case, as Harvard endocrinologist George Cahill suggested, the “nonappetizing nature” of this meat-egg-and-cheese diet will overcome the urge to amply satisfy their desire for food. Our subjects will voluntarily starve themselves, as though hunger itself, and all its regrettable side effects, have been rendered impotent in the face of monotony, which is to say, a diet that these experts define as unappetizing because it does not allow consumption of starches, flour, sugar, or beer.

But Keys had also severely restricted the choice of foods he fed his subjects. Remember, he had wanted to simulate the foods available during wartime in Eastern Europe and so had allowed his conscientious objectors only bread, potatoes, cereals, turnips, cabbages, and “token” amounts of meat and dairy products. Yet, in the entire fourteen hundred pages of his Biology of Human Starvation, there is not the slightest hint that his semi-starved subjects, or those starving populations he discusses in his comprehensive history of famine, would have turned down more cabbages, bread, or turnips had they been available, not to mention meat, cheese, fish, or eggs. The notion that hunger can be relieved or eliminated simply by limiting the choice of food is exceedingly difficult to embrace.

Over the years, a common way to avoid thinking about the paradox of a diet that allegedly restricts calories but does not induce hunger is to attribute the suppression of appetite to a factor that these authorities consider irrelevant to the bigger picture of weight and health—to ketosis, the condition produced when the liver increases its production of ketone bodies to replace glucose as a fuel for the brain and nervous system. Once ketone bodies are produced, “their appetite-depressing activity takes effect,” as Richard Spark of Harvard Medical School claimed in 1973. “Substances called ketones will accumulate in your bloodstream [during carbohydrate restriction] and can make you slightly nauseated and light-headed and cause bad breath,” wrote Jane Brody in the New York Times in 1996. “This state is not exactly conducive to a hearty appetite, so chances are you will eat less than you might otherwise have of the high-protein, high-fat foods permitted on the diet.”