On p. 265 of McDougall's book he says...
...there's no pussyfooting around. Your body loves fat; it's a treasure your system would rather hoard than burn, so if it senses there's any other fuel at hand, it will use that first and convert the leftovers into more fat. To free himself from the sugar-burn cycle, Stu would have to go cold turkey: he could stuff himself silly all day, but only on meat, fish, eggs, avocados, vegetables, and nuts. No beans, no fruit, no grains. No soy, no wine, no beer. Whole dairy like sour cream and real cheese were in; low-fat milk was out.
That was part 1. Part 2 was even more basic: Slow down! When you sprint, Phil explained, you jack up your heart rate. Your body interprets a hammering heart as EMERGENCY! so it goes looking for those gas-soaked rags. It wants the fastest-burning fuel it can find, and that is sugar. But once you've conditioned your body to rely on fat, you'll be able to run as fast as ever - and much faster. For Stu to keep his heart rate in his fat-burning zone, Phil had an easy formula: just subtract your age from 180. Stu was thirty-two years old, so Phil gave him a heart-rate monitor and set it for 153 beats per minute (148 plus five bonus beats because Stu was a highly conditioned athlete). Anytime the monitor beeped, it meant Stu had to slow to a walk until his pulse eased back own.
And it goes on. And I will hopefully go on eventually too. You can click the above link for the MAF Method. However, basically, the way to healthier living and more endurance boils down to two things:
1. Cut out sugar.
2. Slow down my running (so I can go faster).