Good Calories, Bad Calories

The implication is that we will experience no hunger if we eat nothing at all—zero calories—and our cells are fueled by the protein and fat from our muscle and fat tissue. If we break our fast with any amount of dietary protein and fat, we’ll still feel no hunger. But if we add carbohydrates, as Drenick noted, we’ll be overwhelmed with hunger and will now suffer all the symptoms of food deprivation. So why is it when we add carbohydrates to the diet we get hungry, if not irritable, lethargic, and depressed, but this will not happen when we add only protein and fat? How can the amount of calories possibly be the critical factor?

In the early 1950s, Alfred Pennington noted the paradoxes engendered by a diet restricted in carbohydrates and relatively rich in fat and protein, and described them as a “mighty stimulant to thought on the matter.” But this is not how the medical-research establishment has perceived them. Rather, the accepted explanation for the success of carbohydrate-restricted diets is that they work via the same mechanism as calorie-restricted diets—they restrict calories, creating a negative energy balance. Either they so limit the choices of food that dieters simply find it too difficult to consume as many calories as they might otherwise prefer, or they bore the dieters into eating less, or both. “Many individuals spontaneously and unconsciously reduce their energy intakes by as much as 30% when placed on low carb diets,” Johanna Dwyer, a Tufts University nutritionist, explained in 1985. They do this “because there is insufficient carbohydrate permitted for them to eat many common and highly palatable foods in which they might otherwise indulge.” So where’s the paradox?

“The fact remains that some patients have lost weight on the low-carbohydrate diet ‘unrestricted in calories,’” the AMA Council on Food and Nutrition conceded in 1973 in a critique of such diets. “When obese patients reduce their carbohydrate intake drastically, they are apparently unable to make up the ensuing deficit by means of an appreciable increase in protein and fat.” By this logic, weight loss on a diet “unrestricted in calories” does not represent a refutation of the hypothesis that calorie restriction itself—creating a negative energy balance—is the only way to lose weight, because it suggests that a carbohydrate-restricted diet is a calorie-restricted diet in disguise. And the sensation of hunger isn’t an issue, because it can apparently be ignored.^*104

This rationale, which has been invoked frequently over the past four decades, is curious on many levels. First of all, it seems to contradict the underlying principle of low-fat diets for weight control and the notion that we get obese because we overeat on the dense calories of fat in our diets. One reason that bread has always been considered the ideal staple of a low-fat reducing diet, as Jean Mayer noted, is that it only has about sixty calories a slice. “If you put a restaurant-size pat of butter on your toast, for example, you triple the calories,” Mayer said. If we avoid the dense calories of fat in the butter, the argument goes, we will naturally eat fewer total calories and lose weight accordingly. (This was the fallback position in 1984 for the official NIH recommendation of a low-fat diet for heart disease: if nothing else, we’d lose weight on such a diet, and so that would reduce heart-disease risk.) To explain the peculiar efficacy of carbohydrate-restricted reducing diets, the circuitous reasoning is that if we avoid the not-nearly-so-dense calories of bread and potatoes, we will also not consume the dense calories in the butter. We could still eat the dense calories of meat, cheese, and eggs, and we could certainly increase the portion sizes to compensate for the now absent butter, but apparently we won’t want to do that, or somehow won’t be able to, if we don’t have the bread, potatoes, and pasta to eat as well.

Ironically, this argument is based almost exclusively on the research efforts of John Yudkin. “Yudkin showed that a long time ago,” as George Bray recently said. “We don’t generally slice butter off a dish and put in our mouth to eat. We like to put it on bread. That’s why lowering carbohydrates lowers calorie intake.” Yudkin was ridiculed for his advocacy of the hypothesis that sugar causes heart disease. Yet he is considered the essential source for the rationale that reconciles carbohydrate-restricted diets with the conventional wisdom of calories and weight, based on two papers, a decade apart, discussing the experience of seventeen subjects over two weeks of dieting.