Good Calories, Bad Calories

poultry or fish,” and a portion of each of three 5-percent vegetables. Individuals trying to maintain their weight loss could then eat anything else they wanted, Evans wrote, but they could do so only as long as they maintained a stable weight and were sufficiently “sparing with” alcohol, added fats and oils, “concentrated carbohydrate foods,” “starches,” “mealy vegetables, which are potatoes, beans, peas,” and “cereals, used as vegetables, which are: macaroni, spaghetti, rice, corn.”

Evans provided one of the few variations on this regime that caught on as an obesity therapy in the years before World War II. This was a very low-calorie diet, of 360 to 600 calories a day, rather than the common prescription of 1,200 to 1,500 calories, then considered the minimal amount that a patient would tolerate and that would produce a safe and consistent weight loss. Evan’s diet could induce a loss of up to five pounds a week, rather than the two pounds predicted for the more typical semi-starvation diets. The daily menu, explained Evans in 1929, was “composed of fresh meat and egg white. Approximately 100 [grams] of lean steak was the backbone of each of the two largest meals. When necessary, fresh fish was given at intervals.” No starches or sugars were allowed, but the patient could eat a few ounces of 5-percent vegetables and one ounce of bread each day. These minimal carbohydrates—perhaps twenty grams—were included to “spare” the protein in the diet, so that it would be utilized for balancing out nitrogen losses rather than having some of it converted to glucose to fuel the brain and central nervous system. “The secret of the success of this procedure depends, almost certainly, on giving enough protein,” Russell Wilder of the Mayo Clinic wrote after first prescribing the diet for his patients in 1931. Evans’s very low- calorie diet may also have been popular because it appealed to the puritanical sense of those clinicians like Louis Newburgh, who believed that gluttony had to be vigorously curbed in obese patients. One of the fundamental rules of Evans’s diet was: “No concession to gustatory sensualism is permitted.”

In the century before the medical community began prescribing fat-restricted, carbohydrate-rich diets for weight loss, one point of controversy was whether carbohydrates should be avoided because they are uniquely fattening or perhaps even cause obesity—as Jean Anthelme Brillat-Savarin and William Banting would have suggested—in which case they would be the only nutrient restricted, or because they constitute superfluous calories, in which case dietary fat was restricted as well, by avoiding oils, lard, and butter. “The next question to decide,” wrote the Chicago physician Alfred Croftan in the Journal of the American Medical Association in 1906, “is whether the carbohydrates or the fats are to be chiefly restricted.”

One observation made repeatedly through the 1960s was that the obese favor carbohydrates, and that these constitute the great proportion of all calories they consume. Though the obese did not appear to eat more calories, on average, than the lean, they did consume more carbohydrates. Such a dietary assessment was inevitably difficult to make with any accuracy, explained Sir Derrick Dunlop of the Royal Infirmary in Edinburgh, when he reported in 1931 on the lessons he had learned from treating 523 obese patients. Nonetheless, Dunlop believed that “obesity does occur in persons without showing any direct relationship to food intake, and that a certain group of patients do become overweight on an apparently normal well-balanced diet,” and, second, “that an outstanding dietetic abnormality was an excessive intake of carbohydrate.” “In some extreme cases,” he noted, “the diet had consisted almost exclusively of sweet tea, white bread and scones.”

This observation was echoed in The Lancet in 1935 by the British physician John Anderson, and in the 1940s by Hilde Bruch, Hugo Rony, and the Harvard physician Robert Williams and his colleagues, all of whom had questioned their fat patients extensively about their diets. Their common finding was an excessive consumption of starches and sweets. Rony reported that the craving for sweets and starches among his patients was so common that it suggested an underlying physiological mechanism at work, possibly related to a greater need for or reduced availability of glucose. “It is easier to induce the gluttonous obese to control his general appetite than to control his craving for sweets,” Rony noted. One common rationale for restricting carbohydrates in weight-reducing diets was that it eliminated a disproportionately large share of the calories that the obese would normally eat.^*92

When carbohydrates are restricted, however, calories may also be cut—and the reverse is nearly always true. One of the revolutionary aspects of Frank Evans’s very low-calorie diet was that it also restricted carbohydrates almost entirely.^†93 When Louis Newburgh subsequently concluded that all obese patients can sustain a significant rate of weight loss for months or years if their diet is sufficiently draconian—as was the case with his patient who lost over 360 pounds—he was using Evans’s very low-calorie, very low-carbohydrate diet to generate this weight loss. His patient lost the weight while eating at most a hundred calories of carbohydrates daily. It could have been the restriction of carbohydrates that was responsible for the weight loss. It could also have been the calorie restriction.

This same confounding of calories and carbohydrates might also explain the success stories attributed to low- calorie diets—Albert Stunkard’s one patient in a hundred, as he reported in 1959, who lost as much as forty pounds and managed to keep it off. It’s effectively impossible to restrict calories significantly without also reducing the carbohydrates. Any calorie-restricted diet that restricts all calories equally, restricts carbohydrates, too. Even diets that preferentially reduce fat will have to reduce carbohydrates to achieve a significant reduction in calories (unless the dieters are willing to sacrifice protein in fish and meat, for instance, in order to avoid the fat that accompanies it). If dieters avoid sweets and snacks, and if they drink sugar-free soda but not regular soda, they’re reducing their carbohydrate consumption significantly, and they’re changing the type of carbohydrates they consume. Any benefit may be due to the calories reduced, or the carbohydrates, or even just the relative absence of sugar.

Another issue that complicates this issue of calorie versus carbohydrate restriction is that the effect of weight- loss diets changes over time. The modest benefits of semi-starvation slowly diminish with time, as the calorie restriction induces a compensatory inhibition of energy expenditure. Moreover, much of the initial weight loss comes from losing water, not fat (see Chapter 8). Because of this “tendency to retain water on a carbohydrate diet and to give it out on a rich fat diet,” as Dunlop described it, restricting carbohydrate calories specifically will induce a more dramatic and immediate loss of water. Testing diets for only a few weeks will demonstrate that carbohydrate- restricted diets induce weight loss at a greater rate than calorie-or fat-restricted diets, but whether they induce fat loss at a greater rate is a different question. “Changes in body-weight are to be taken, therefore, as of significance only when the experiment continues for a period of several weeks,” as Francis Benedict cautioned in 1910. “Certainly, for short experiments, body-weight is for the most part wholly without significance.”

For this reason, the first meaningful report on the efficacy of carbohydrate restriction for weight loss was one published in 1936, by Per Hanssen of the Steno Memorial Hospital in Copenhagen. Hanssen reported treating twenty-one obese patients over two years with an 1,850-calorie diet that contained only 450 calories of carbohydrates, or a little less than 25 percent. Nearly 60 percent of the calories came from fat: 65 grams of cream, 65 grams of butter, and 25 grams of olive oil every day, along with two eggs, cheese, and a liberal portion of meat or fish. Some of his patients, Hanssen reported, were so fat initially that they “could scarcely move when they arrived at the hospital, and were unable to work.” On the diet from one to four months, the patients lost an average of two pounds a week. “During the stay in the hospital the patients never felt hungry,” he reported. “The fatigue, a prominent and disturbing symptom, improved often very rapidly, and before the occurrence of any considerable reduction in weight.” Hanssen compared his results with those reported five years earlier by physicians at the nearby University Clinic using a diet consisting of half the calories but twice the proportion of carbohydrates (over 50 percent). “At Steno Memorial Hospital,” Hanssen noted, “a diet of 1,850 calories will reduce weight as quickly as a diet of 950 calories at the University Clinic of Copenhagen.”

If obese individuals can lose weight and keep it off, without hunger, on a diet of 1,850 calories, it’s a reasonable assumption that they will find it easier to sustain such a diet than one that allows only 950 calories, or even less, and assumes, as Evans put it, that the obese “should be hungry most of the time as this is normal.” A diet “relatively poor in carbohydrates,” Hanssen suggested, might “not be so difficult to adhere to as the diets