Read the studies (or even look at the abstracts)in the medically supported journals which are supplied in said book. Or search your own. There is near zero legit data for calories in calories out hypothesis. The body does not function like a simple machine being fed fuel, it will expend more or severely conserve depending on the situation. Dr Jason Fung and other physicians are changing the weight loss game. Many obstinate docs have resisted the evidence and are now changing their tune, bc there is nothing to support calories in/out. The obesity Cody theories have the best data to this date, and will be the way of future for: weight loss, control/elimination of diabetes and hypertension reduction etc, etc. It’s gaining steam and being implemented in the medical community and by many of my colleagues.