Good Calories, Bad Calories

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 Sjövall 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. Peña 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.