Good Calories, Bad Calories

Through the 1950s, the carbohydrate-restricted diet had challenged only the positive-caloric-balance hypothesis of obesity. Yudkin had managed to reconcile carbohydrate restriction with this conventional wisdom by insisting that low-carbohydrate diets were low-calorie diets in disguise. By doing so, Yudkin made the diets politically acceptable, although he also directed attention away from the underlying science. In the same 1960 Lancet article in which Yudkin proclaimed what he called “the inevitability of calories,” he had made the point that if the diet was indeed low in calories, then its fat content would also be comparatively low, reconciling his diet with Keys’s dietary-fat hypothesis. This was Yudkin’s “no bread, no butter” argument. If carbohydrate calories are restricted, fat calories are, too. Though the proportion of fat in the diet increases if carbohydrates are avoided, the absolute quantity of fat may actually decrease. This is why Yudkin insisted that the correct terminology for these diets should be “low-carbohydrate” rather than “high-fat.” “It is highly implausible,” Yudkin wrote in 1974, “that a given amount of fat that is harmless when energy intake is excessive becomes harmful when this excess is corrected by a reduction in the intake of sugar and starch.”

As a result of Yudkin’s conciliatory efforts, the only carbohydrate-restricted diets that elicited a backlash from nutritionists were those promoted by clinicians whose interpretation of the science disagreed with Yudkin’s. This situation was exacerbated by the fact that it was these physicians, without university affiliations, who adopted the diet quickly and then wrote books for the lay public that sold exceptionally well. Because their claims sounded like quackery—The High-Calorie Way to Stay Thin Forever, as Dr. Atkins’ Diet Revolution was subtitled—they were treated as such, and particularly so after the medical and public-health authorities decided that dietary fat might cause heart disease.

The small contingent of influential nutritionists from Fred Stare’s department at Harvard provide an example of how this process of entrenchment evolved. In 1952, when Alfred Pennington lectured at Harvard on the benefits of carbohydrate restriction and Keys was only beginning his crusade against dietary fat, Mark Hegsted had suggested, “Dr. Pennington may be on the right track in the practical treatment of obesity.” A decade later, and a year after the American Heart Association had officially sided with Keys, the Brooklyn obstetrician Herman Taller published his best-seller, Calories Don’t Count, based on Pennington’s work and Taller’s clinical experiences with the diet. Stare called the book “trash,” and Jean Mayer described the high-fat aspect of the diet as “potentially dangerous.” Philip White, who received his doctorate in nutrition from Stare’s department, then wrote a review of Calories Don’t Count for JAMA, accusing Taller of perpetrating “nutrition nonsense and food quackery.” In 1973, in response to the publication of Dr. Atkins’ Diet Revolution, based on Atkins’s clinical experience with overweight patients and another decade of science, White edited a critique of carbohydrate-restricted diets in JAMA—the first draft of which was written by Ted Van Itallie, another veteran of Stare’s nutrition department—that now dismissed the diets as “bizarre concepts of nutrition and dieting [that] should not be promoted to the public as if they were established scientific principles.”

Meanwhile, these nutritionists would readily admit that they didn’t know what caused obesity (why some people ate too much and others didn’t) and that calorie restriction conspicuously failed to cure it. After nearly twenty years in the field, as Jean Mayer wrote in the introduction to his 1968 monograph, Overweight, he was “as aware as any man of the gigantic gaps in our knowledge—and of the likelihood that many of our present concepts may be erroneous.” He also noted, in his discussion of hormonal influences on obesity, that insulin “favors fat synthesis” and that someone who over-secretes insulin could “tend to become hungry as a result.” But when a physician suggested publicly, as Atkins did, that carbohydrates raised insulin levels, that insulin favors fat synthesis, and that a diet lacking carbohydrates might reverse this process, these nutritionists would denounce it, as Mayer himself did in 1973, as “biochemical mumbo-jumbo.”

With the publication of Dr. Atkins’ Diet Revolution and its subsequent censure by the American Medical Association, the nature of the professional discussions on carbohydrate-restricted diets turned from their clinical utility to the reasons to avoid them. The actual science suddenly mattered less than ever.