THE AMERICAN HEART ASSOCIATION TODAY insists that severe carbohydrate restriction in a weight-loss diet constitutes a “fad diet,” to be taken no more seriously than the grapefruit diet or the ice-cream diet. But this isn’t the case. After the publication of Banting’s Letter on Corpulence in 1863, physicians would routinely advise their fat patients to avoid carbohydrates, particularly sweets, starches, and refined carbohydrates, and this practice continued as the standard treatment of obesity and overweight through the better part of the twentieth century. Only after the AHA itself started recommending fat-restricted, carbohydrate-rich diets for heart disease in the 1960s and this low-fat prescription was then applied to obesity as well, was carbohydrate restriction forced to the margins. “In the instruction of an obese patient,” as Louis Newburgh of the University of Michigan explained in 1942, “it is a simple matter to teach him to omit sugar because sweet flavors are not easily disguised. It is also relatively simple to teach him to limit the use of foods high in starch.”

Those early weight-loss diets were meant to eliminate fat tissue while preserving muscle or lean-tissue mass. The protein content of the diet would be maximized and calories reduced. Only a minimal amount of carbohydrates and added fats—butter and oils—would be allowed in the diet, because these were considered the nonessential, i.e., nonprotein, elements. When physicians from the Stanford University School of Medicine described the diet they prescribed for obesity in 1943, it was effectively identical to the diet prescribed at Harvard Medical School and described in 1948, at Children’s Memorial Hospital in Chicago in 1950, and at Cornell Medical School and New York Hospital in 1952. According to the Chicago clinicians, the “general rules” of a successful reducing diet were as follows:

1. Do not use sugar, honey, syrup, jam, jelly or candy.

2. Do not use fruits canned with sugar.

3. Do not use cake, cookies, pie, puddings, ice cream or ices.

4. Do not use foods which have cornstarch or flour added such as gravy or cream sauce.

5. Do not use potatoes (sweet or Irish), macaroni, spaghetti, noodles, dried beans or peas.

6. Do not use fried foods prepared with butter, lard, oil or butter substitutes.

7. Do not use drinks such as Coca-Cola, ginger ale, pop or root beer.

8. Do not use any foods not allowed on the diet and [for other foods use] only as much as the diet allows.

With the carbohydrates and added fats minimized in these diets, meat was inevitably the primary constituent. This would provide the protein necessary to ensure that weight loss came mostly from the patient’s fat and not the muscle. The idea was to keep the body in what is called nitrogen equilibrium, with the nitrogen consumed from the protein in the diet balancing out the nitrogen being excreted in the urine from the breakdown of muscle protein.