Good Calories, Bad Calories (74 page)

Between 1973 and the mid-1980s, the notion of the fattening carbohydrate, which had persisted in clinical and popular literature for wel over a century, was replaced with the belief that it is dietary fat, with its particularly dense calories, that is responsible for overweight and obesity. The prescription of reducing diets that restricted starches and sugars, and perhaps oils and butter as wel , was replaced with diets that targeted fat alone—restricting not just butter and oils but meat, eggs, and dairy products—thereby increasing carbohydrate consumption. Obesity was conceptual y transformed from a condition commonly associated with the excessive consumption of carbohydrates and carbohydrate craving to one that would be described by prominent nutritionists as a “carbohydrate-deficiency syndrome,” which in turn explained why “an increase in dietary carbohydrate content at the expense of fat is the appropriate dietary part of a therapeutical strategy.”

What makes this shift al the more perplexing is that it occurred immediately after the science of fat metabolism evolved to explain why carbohydrates were uniquely fattening, and it fol owed a six-year period in which carbohydrate-restricted diets achieved unprecedented credibility among clinicians. The latter coincided precisely with the genesis of obesity research as what would be considered a legitimate field of scientific study, a transformation marked by the increasingly frequent appearance of conferences and symposiums dedicated to reporting the latest findings in obesity research, al of which, through 1973, had been dominated by discussions of the peculiar efficacy of carbohydrate-restricted diets.

The first was hosted by the University of California, San Francisco, in December 1967. Among the dozen speakers was the veteran UC Berkeley nutritionist Samuel Lepkovsky, who used exactly the same logic as Alfred Pennington had in the 1950s to argue the biological rationale of carbohydrate restriction. “Positive caloric balance may be a result rather than a cause of the [obese] condition,” Lepkovsky said. “It seems desirable in the treatment of obesity to direct efforts toward an increased utilization of fat. This effort can be made by restricting the intake of carbohydrates and increasing the ingestion of fat.” The one presentation at the conference that was specifical y on the dietary treatment of obesity came from a team of U.S. Navy physicians, who had been prescribing an eight-hundred-to-one-thousand calorie “ketogenic” diet to overweight naval personnel. Their diet was 70 percent fat, 20 percent protein, and 10 percent carbohydrate, and it induced “significant weight loss” in al their patients. “Uniformly and without exception,” they added, “patients who underwent dieting found that the satiety value of the ketogenic diet was far superior to that of a mixed or high-carbohydrate diet, even though the food selection was minimal….”

In 1968, the newly founded Obesity Association of Great Britain hosted in London its first symposium on obesity. The presentations were dominated by investigators who believed in the fattening nature of carbohydrates and the efficacy of carbohydrate-restricted diets. These included John Yudkin and his col eague Stephen Szanto; W.J.H. Butterfield, who would later become vice-chancel or of the University of Cambridge; Alan Kekwick and Gaston Pawan of the University of London, who were primarily responsible for reviving the concept of Banting’s diet in the U.K.; and Denis Craddock, a general practitioner and author of Obesity and Its Management, which would be published in 1969 and was one of at most two or three clinical guides to obesity treatment published in the U.K. in the 1960s or 1970s. As Craddock reported at the conference, he had recently completed a survey of a hundred pregnant patients, sixty of whom had begun to fatten excessively during the early months of their pregnancy. “This weight gain was control ed in most cases”—fifty-seven of the sixty—“simply by restricting carbohydrates in the diet,” he said.

The conference had been organized by Alan Howard and his col eague Ian McLean Baird. Howard was a biochemist and pathologist at the University of Cambridge who would later become the founding editor, with George Bray, of the International Journal of Obesity. Howard had become interested in carbohydrate restriction because he had been twenty pounds overweight, had unsuccessful y dieted for years, then final y lost the weight and kept it off by avoiding flour, starches, and sweets. At the London conference, Howard reviewed the literature on carbohydrate restriction dating back to Banting and concluded that this was the only effective method to induce and maintain weight loss. “A common feature of al who have written on the subject,” he said, is “that the patient’s hunger is satisfied whilst on a diet high in carbohydrate of the same caloric value, patients complain of hunger.”

After the London meeting, obesity conferences evolved from local to international affairs. The first was in Paris in 1971, hosted by European nutrition and dietetics associations. Here the sole presentation on the dietary treatment of obesity was by a col aboration from the French National Institute on Health and Medical Research (INSERM), which is the local counterpart of the NIH in the United States and the Medical Research Council in the United Kingdom. These INSERM investigators had prescribed diets of twelve to eighteen hundred calories to over a hundred obese patients, in either three or seven meals a day, and with varying amounts of carbohydrates. Weight loss increased, they reported, when the subjects divided their calories among seven meals, which served to moderate the insulin response. Moreover, “lowering the carbohydrate content of the diet increased the weight loss at both meal frequencies.”

The next conference was hosted by the NIH in Bethesda, Maryland, in October 1973. Six of the presentations at this meeting discussed the treatment of obesity by methods other than drugs or surgery. Two were on physical activity, and neither reported any significant effect of exercise on body weight. Two addressed the benefits of behavioral modification on weight loss, and neither reported any significant benefit. Of the two remaining presentations, one was by Ernst Drenick of UCLA on prolonged fasting to treat obesity—“our experiences are disappointing,” said Drenick—and the other was by Charlotte Young of Cornel on dietary treatments.

As Howard had in London, Young reviewed the hundred-year history of carbohydrate-restricted diets, including the research of Pennington and that of Margaret Ohlson and her own trials in the 1950s. Young then discussed her recent studies, in which she had put obese young men on eighteen-hundred-calorie diets with the protein content fixed at 460 calories (26 percent), but with varying proportions of fat and carbohydrates. Over the course of nine weeks, she reported, “weight loss, fat loss, and percent weight loss as fat appeared to be inversely related to the level of carbohydrate in the diets”—in other words, the fewer carbohydrates and the more fat in the diet, the greater the weight loss and the greater the fat loss. “No adequate explanation could be given for the differences in weight losses,” she said. Al of the carbohydrate-restricted diets, she said, “gave excel ent clinical results as measured by freedom from hunger, al aying of excessive fatigue, satisfactory weight loss, suitability for long term weight reduction and subsequent weight control.”

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 specifical y as the cause of obesity. Lester Salans and Edward Horton, both col aborators 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 wil “reduce superfluous adiposity,” Yudkin said, “but it wil 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 chronical y 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 mel itus and of a number of other conditions.” Keen and his col eagues 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 equal y 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 al owed liberal fat consumption was to be considered unhealthy. Clinical investigators working on the problem of human obesity concurred.

Through the 1950s, the carbohydrate-restricted diet had chal enged 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 political y acceptable, although he also directed attention away from the underlying science. In the same 1960 Lancet article in which Yudkin proclaimed what he cal ed “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 actual y 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 exceptional y wel . 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 smal 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 official y sided with Keys, the Brooklyn obstetrician Herman Tal er published his best-sel er, Calories Don’t Count, based on Pennington’s work and Tal er’s clinical experiences with the diet. Stare cal ed the book “trash,” and Jean Mayer described the high-fat aspect of the diet as “potential y 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 Tal er 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 Ital ie, 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.”