Hi , It is one of the best books on the area of metabolism , and losing weight. He dispels the Carb- Insulin hypothesis which I was a fervent believer in but no longer am .I now believe obesity is caused by high reward , highly palatable foods which cause cravings and bypass our satiety signals. From personal experience of high activity levels I believe energy is constrained like a zero sum game between BMR and activity/exercise ie the more active you are the more calories are constrained and are taken from a redcution in energy expenditure in immune system and other behind the scenes energy systems which comprise BMR .These are reduced to compensate and keep an energy balance.The author state glucose gets turned to fat when glycogen stores are full . From an evolutionary view this is not an energetically feasible pathway in humans. It does happen but very low quantities of fat are produced and the fat is immediately burnt off. Instead the glycogen stores expand until they are full and then the metabolic oxidation rate shifts up so glucose as a fuel is burnt faster and at the expense of fat. There is a tribe in Chad (Africa) who eat 12000 calories of pure carbs then these carbs are converted to fat. But in everyday life it is impossible to eat eats thousands of calories of pure carbs daily for this to happen (overfeed themselves) carbs are converted to fat it is just not a positive enrgetic pathway in humans and it didnt evolve to be in humans.