Physicians were slow to appreciate that insulin allowed the proportion of carbohydrate in the diet to be increased, for, as Himsworth said, ‘a well-founded theory directs that the carbohydrates in the diabetic’s diet must be curtailed if health is to be preserved’. On the other hand, as he continued, ‘a brilliant piece of clinical empiricism produces irrefutable proof that a liberal allowance of carbohydrate acts favourably on the diabetic’s health’ [17]. This empiricism began in 1926, when a high carbohydrate diet was first shown to improve glucose tolerance in healthy individuals [18]. Noting this, William Sansum promptly increased the carbohydrate content of the diet of his Californian patients; a typical recommendation might include 2,435 calories, 245 g of carbohydrate (40% of energy requirements), 124 g of fat and 100 g of protein [19].