‘You can’t outrun a bad diet,’ McDougall writes. ‘No matter how many miles you put in, you’ll continue to store body fat, as long as your eating causes your blood sugar to spike.’ He recommends a food regime called the Maffetone method, based on the research of nutritionist Phil Maffetone. It urges runners to think of their body as a furnace. Fill up the furnace with slow-burning logs and it will run ‘smooth and strong for hours’. But, if you load the furnace with paper and petrol-soaked rags, it will ‘burn hot, rattle the pipes, and die out until it’s fed again’.
For that reason, McDougall suggests runners embark on Maffetone’s two-week test to restore their natural metabolism. ‘You’ll crave better foods because they’ll make you feel good, instantly,’ he writes. ‘You’ll turn healthy eating back into an intrinsic pleasure.’