Good Calories, Bad Calories

The last of these conferences to be held before the nutritional wisdom began to shift definitively was in London in December 1973, just two months after the NIH meeting. This one was organized by Yudkin, and many of those giving presentations had also attended the NIH conference. Their presentations were similar, but here there was more of a tendency to implicate carbohydrates specifically as the cause of obesity. Lester Salans and Edward Horton, both collaborators of Ethan Sims on his experimental obesity studies, discussed the effect of carbohydrates on hyperinsulinemia and the role of hyperinsulinemia in obesity. “It is clear that in both lean and obese subjects the carbohydrate content of the diet influences…insulin and glucose concentrations,” Horton reported. He added that it was probably hyperinsulinemia that induced both obesity and insulin resistance. Yudkin then gave the only talk on dietary therapy, entitled “The Low-Carbohydrate Diet,” noting that these diets are higher in vitamins and minerals than calorie-restricted diets, simply because the foods restricted—starches and sugars—have few or no vitamins and minerals. The diet will “reduce superfluous adiposity,” Yudkin said, “but it will not need to be changed when this has been done…. The diet is intended as anew but permanent pattern of eating and not simply as a cure for obesity, to be abandoned when an acceptable loss of weight is achieved.” Harry Keen, who was then at Guy’s Hospital Medical School and would become one of the most influential diabetologists in the U.K.,^*122 said the critical issue wasn’t just obesity, but the chronic diseases that accompanied it. “With the chronically failed case of obesity we are dealing with the wreckage of the situation,” he said, so it was necessary to set “new patterns of body weight and body size, if we are going to make a serious attempt to reduce the frequency, for example, of atherosclerosis, of diabetes mellitus and of a number of other conditions.” Keen and his colleagues had tested the viability of this goal, he reported, on a group of “ostensibly normal men in whom obesity is represented no more frequently than in the population at large.” These men were instructed to restrict their carbohydrate intake to less than five hundred calories a day, but to continue eating protein and fat as desired. The result was an average weight loss of fourteen pounds, impressive because these individuals were not necessarily overweight to begin with. That weight loss had been maintained for almost five years. To those who might be pessimistic about the prevention of obesity and overweight in the public at large, Keen said, this result should be taken as “a word of reassurance and optimism.”

By 1972, The New York Times Natural Foods Dieting Book was offering both a low-calorie weight-loss plan, at a thousand calories a day, and a low-carbohydrate method. “You strictly curtail the amount of carbohydrates you eat daily,” the book explained. “You eat, instead, foods in which the carbohydrate content is very low or nonexistent. Meat…fish, poultry, fats, butter, most cheeses and eggs are equally low in that fattening substance, and these are the foods that form the basis for your diet…for without carbohydrates you cannot gain weight!”

Two years later, when the nonprofit organization Consumer Guide published its first edition of Rating the Diets, a 380-page compendium of the pros and cons of popular diets, carbohydrate restriction seemed firmly established in the canon. Rating the Diets, which obesity authorities would repeatedly recommend as a valuable review of the evidence, concluded that a diet including less than sixty grams of carbohydrates each day had “much to recommend it” and so was “helpful and beneficial” for weight loss. It also quoted a medical textbook to the effect that “the difficult-to-treat obese patient,” which effectively means every obese patient, “appears to suffer from some defect in dealing with carbohydrate which leads to an unnatural conversion of it to fat and to storage of the fat. Avoidance of too much dietary carbohydrate reduces this tendency.” The only caveat with these diets, according to Rating the Diets, was that they “pay little attention to the kinds of fats you eat” and so might increase heart-disease risk.

The shift in the nutritional wisdom was now taking place, driven by the contagious effect of Ancel Keys’s dietary-fat/heart-disease hypothesis on the closely related field of obesity. Any diet that allowed liberal fat consumption was to be considered unhealthy. Clinical investigators working on the problem of human obesity concurred.