Toward the end of the First World War, a Long Island doctor named Blake Donaldson rediscovered carbohydrate restriction somewhat independently of his predecessors. Frustrated by his failure at helping patients lose weight with the “eat less, move more” method, he was hungry for a better approach. Donaldson found his ears perking up during a tour of the American Museum of Natural History, where he was informed that the indigenous Inuit population, apparently a model of active lifestyles and exemplary health, seemed to live on nothing but fatty cuts of meat. In the decades that followed, Donaldson treated thousands and thousands of patients. Not only did he report them to lose roughly 3 lbs a week without feeling deprived, but they could keep their weight controlled long term.

In 1944, Donaldson gave a lecture about his work at a hospital in New York that would greatly influence an incredibly influential person. That man in the audience was Alfred Pennington, the in-house physician for the DuPont chemical corporation. DuPont, like many American corporations of the era, had a boardroom full of middle-aged, overweight executives who were dying of heart diseases at an alarming rate. Pennington selected 20 of these gentlemen to participate in a monitored diet that was restricted in carbohydrates but not calories.

While the war had truncated the progression of European science and effectively made English the language of science globally, Pennington discovered that the hypothesis he was looking for already existed: the German and Austrian researchers had developed a hormonal theory of fat storage. The theory held, broadly speaking, that not all types of calories have the same effect on human hormones, which must bear a critical role in metabolism, specifically whether fat is stored and locked away or mobilized and burned for fuel.

In 1972, a cardiologist named Dr Atkins presented the low-carbohydrate, high-fat (LCHF) way of eating to the American public all over again in his Dr Atkins’ Diet Revolution, a book for the mainstream that sensationalized the issue (even by its very title). Atkins himself treated thousands of his patients with the diet, but this made little impact on the opinions of his detractors.

By this point, the lines were drawn: for the proponents of LCHF benefits, from weight loss to beyond, the proof was in the pudding, and the results were plain to see, indeed undeniable. For the skeptics, the recommendation to reduce carbohydrates and embrace fats was “the equivalent of mass murder,” as described memorably in 1965 by Harvard’s Jean Mayer, one of America’s foremost nutrition professionals.