Good Calories, Bad Calories

Bistrian of MIT’s department of nutrition and food science and the Harvard Medical School in the 1970s. Wilder was treating his obese patients with the very low-calorie diet developed by Frank Evans, principally meat, fish, and egg white, with 80–100 calories’ worth of green vegetables. “The absence of complaints of hunger has been remarkable,” Wilder wrote. Bistrian and Blackburn reported in 1985 that they had prescribed their diet of lean meat, fish, and fowl—almost 50 percent protein calories and 50 percent fat—to seven hundred patients. On average, the patients lost forty-seven pounds over a period of four months; nearly three pounds a week. “People loved it,” said Blackburn.^†102

Significant weight loss without hunger was also reported when the diet was prescribed at 1,000 calories, as the University of Wurzburg clinicians Heinrich Kasper and Udo Rabast did in a series of trials through the 1970s; at 1,200 calories, as the University of Iowa nutritionist Willard Krehl reported in 1967; at 1,320 calories, as Edgar Gordon of the University of Wisconsin reported in JAMA in 1963; at 1,400 or 1,800 calories, as Young and Ohlson did; at 2,200 calories, as the Swedish clinician Bertil Sjovall reported in 1957, and even when the diet provided more than 2,700 calories a day, as reported also in 1957 by Weldon Walker, who would later become chief of cardiology at the Walter Reed Army Medical Center in Washington. The same has invariably been the case even when patients are simply “encouraged to eat as much as [is] necessary to avoid feeling hungry,” but to avoid carbohydrates in doing so, as John LaRosa, now president of the State University of New York Downstate Medical Center, reported in 1980.

Every investigator who compared these carbohydrate-restricted diets with more balanced low-calorie diets also reported that the carbohydrate-restricted diet performed at least as well, and usually better, even when the caloric content of the carbohydrate-restricted diet was significantly greater—say, 1,850 calories versus 950 calories, as Per Hanssen reported in 1936; or 2,200 calories versus 1,200 calories, as Bertil Sjovall reported in 1957; or even an “eat as much as you like” diet compared with a 1,000-calorie diet, as Trevor Silverstone of St. Bartholomew’s Hospital in London reported in 1963 in a study of obese diabetics. The same held true for children, too. In 1979, L. Pena and his colleagues from the Higher Institute of Medical Sciences in Havana reported that they had randomized 104 obese children to either an “eat as much as you like” high-fat, high-protein diet with only 80 calories of carbohydrates, or an 1,100-calorie diet of which half the calories came from carbohydrates. The children on the carbohydrate- restricted diet lost almost twice as much weight as those who were semi-starved on the balanced diet.

Between 1963 and 1973, Robert Kemp, a physician at Walton Hospital in Liverpool, published three articles reporting his clinical experience with a low-carbohydrate, unrestricted-calorie diet. Kemp reported that his obese patients craved carbohydrates and were invariably puzzled and frustrated by two aspects of their condition: “that other people can eat just the same diet and remain thin,” and “that they themselves in earlier life may well have been thin on the same amount and type of food on which they subsequently became fat.” These observations led Kemp to formulate “a working hypothesis that the degree of tolerance for carbohydrate varies from patient to patient and indeed in the same patient at different periods of life.” He then translated this hypothesis into a carbohydrate-restricted, calorie-unrestricted diet. Doing so, he said, made it “possible for the first time in [his] experience to produce worth-while results in obesity treatment.”

Beginning in 1956, Kemp prescribed this diet to 1,450 overweight and obese patients. More than seven hundred (49 percent) were “successfully reduced” in his practice, which Kemp defined as having lost more than 60 percent of their excess weight. These patients averaged twenty-five pounds of weight loss after a year on the diet. Another 550 patients (38 percent) defaulted, which means they stopped appearing at Kemp’s monthly counseling sessions. Nearly two hundred patients (13 percent) failed to lose significant weight while apparently following through with the treatment. This failure suggested to Kemp that the diet may not work on everyone, despite some claims by popular diet books that it can.

Still, even if we assume that all of Kemp’s patients who defaulted on the diet also failed to lose significant weight, Kemp’s track record would still suggest that his carbohydrate-restricted diet was at least four times more effective than the balanced semi-starvation diet that Albert Stunkard used when reporting on his clinical experiences in 1959.

The last decade has witnessed a renewed interest in testing carbohydrate-restricted diets as obesity levels have risen and a new generation of clinicians have come to question the prevailing wisdom on weight loss. Six independent teams of investigators set out to test low-fat semi-starvation diets of the kind recommended by the American Heart Association in randomized control trials against “eat as much as you like” Pennington-type diets, now known commonly as the Atkins diet, after Robert Atkins and Dr. Atkins’ Diet Revolution. Five of these trials tested the diet on obese adults, one on adolescents. Together they included considerably more than six hundred obese subjects. In every case, the weight loss after three to six months was two to three times greater on the low-carbohydrate diet—unrestricted in calories—than on the calorie- restricted, low-fat diet.

In 2003, seven physicians from the Yale and Stanford medical schools published an article in JAMA that claimed to be the “first published synthesis of the evidence” in the English- language medical literature on the efficacy and safety of carbohydrate-restricted diets. These doctors concluded that the evidence was “insufficient to recommend or condemn the use of these diets,” partly because there had been no long-term randomized controlled trials that established the safety of the diets. Nonetheless, they did report the average weight loss from the trials that the authors had culled from the last forty years of medical research. “Of the 34 of 38 lower-carbohydrate diets for which weight change after diet was calculated,” they noted, “these lower-carbohydrate diets were found to produce greater weight loss than higher-carbohydrate diets”—an average of thirty-seven pounds when carbohydrates were restricted to less than sixty grams a day, as Pennington had prescribed, compared with four pounds when they were not.^*103

Accepting that high-calorie diets can lead to greater weight loss than semi-starvation diets requires overturning certain common assumptions. One is that a calorie is a calorie, which is typically said to be all we need to know about the relationship between eating and weight. “Calories are all alike,” said the Harvard nutritionist Fred Stare, “whether they come from beef or bourbon, from sugar or starch, or from cheese and crackers. Too many calories are too many calories.” But if a calorie is a calorie, why is it that a diet restricted in carbohydrates—eat cheese, but not crackers—leads to weight loss, largely if not completely independent of calories? If significant weight can be lost on all these carbohydrate-restricted diets, even when subjects eat twenty-seven hundred or more calories a day, how important can calories be to weight regulation? Wouldn’t this imply that the quantity of carbohydrates is at least a critical factor, in which case there must be something unique about these nutrients that affects weight but falls outside the context of energy content? Isn’t it possible, as Max Rubner suggested a century ago, that “the effect of specific nutritional substances upon the glands” might be a factor when it comes to weight regulation, and perhaps the more relevant one?

Look at this another way. When Bruce Bistrian and George Blackburn instructed their patients to eat nothing but lean meat, fish, and fowl—650 to 800 calories a day of fat and protein—half of them lost at least forty pounds each. That success rate held true for “thousands of patients” from the 1970s on, Bistrian said. “It’s an extraordinarily effective and safe way to get large amounts of weight loss.” But had they chosen to balance these very low-calorie diets of fat and protein with carbohydrates—say, by adding another 400 calories of “wonderful fruits and vegetables,” as Bistrian phrased it—they would then be consuming the kind of semi-starvation diet that inevitably fails: 1,200 calories evenly balanced between protein, fat, and carbohydrates. “The likelihood of losing forty pounds on that diet is one percent,” Bistrian said.

The bottom line: If we add 400 calories of fat and protein to 800 calories of fat and protein, we have a 1,200- calorie high-fat, carbohydrate-restricted diet that will still result in considerable weight loss. If we add 400 calories