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.”