Good Calories, Bad Calories

McGovern asked Cooper if he could, at least, agree with the proposition that “overconsumption may be as serious a problem of nutrition as under-consumption.”

“Particularly overconsumption of the wrong things,” Cooper replied. “Very often in the poor we see people who are plump who might be called obese, and people would then conclude that they do not have a deficiency because they look rotund, healthy in one sense of the word. But it is true that the consumption of high carbohydrate sources with the induction of obesity constitutes a very serious public health problem in the underprivileged and economically disadvantaged. I would agree with that.”

This response seems clear enough: the overconsumption of “high carbohydrate sources”—a phrase used to describe carbohydrate-dense starches and refined carbohydrates rather than leafy green vegetables and fruits—was associated with obesity in the poor, and perhaps even the cause. McGovern then asked Cooper to provide a “general rule of thumb” about eating habits that would help prevent disease and lengthen our lives, and Cooper reluctantly agreed to do so.

“What kinds of foods in general should we be consuming less of and what should we be eating more of?” McGovern asked.

“I think what we need to consider doing is to reduce our total fat intake,” Cooper replied. “Fat adds a caloric substance—almost twice as much—nine calories per gram—as compared to sugar. I think in order to have an effective reduction in weight and realignment of our composition we have to focus on reducing fat intake.”

With that answer, Cooper had contradicted himself, and the conventional wisdom on diet and health in America had shifted. The problem was no longer overconsumption of high-carbohydrate sources, but the overconsumption of fatty foods. And if Cooper realized that reducing our total fat intake meant increasing our consumption of carbohydrates, he neglected to say so.

Between 1973 and the mid-1980s, the notion of the fattening carbohydrate, which had persisted in clinical and popular literature for well 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 well, 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 conceptually 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 all the more perplexing is that it occurred immediately after the science of fat metabolism evolved to explain why carbohydrates were uniquely fattening, and it followed 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, all 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 specifically 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 all 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 colleague Stephen Szanto; W.J.H. Butterfield, who would later become vice-chancellor 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 controlled 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 colleague 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 unsuccessfully dieted for years, then finally 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 all 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 collaboration 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 Cornell 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