The Obesity Code: Unlocking the Secrets of Weight Loss (Why Intermittent Fasting Is the Key to Controlling Your Weight)

by Jason Fung

Let’s take an example. Suppose our body set weight is 200 pounds (approximately 90 kilograms). By restricting calories, we will briefly lose weight—say down to 180 pounds (approximately 81 kilograms). If the body set weight stays at 200 pounds, the body will try to regain the lost weight by stimulating appetite. Ghrelin is increased, and the satiety hormones (amylin, peptide YY and cholecystokinin) are suppressed. At the same time, the body will decrease its total energy expenditure. Metabolism begins shutting down. Body temperature drops, heart rate drops, blood pressure drops and heart volume decreases, all in a desperate effort to conserve energy. We feel hungry, cold and tired—a scenario familiar to dieters. Unfortunately, the result is the regain of weight back to the original body set weight of 200 pounds. This outcome, too, is familiar to dieters. Eating more is not the cause of weight gain but instead the consequence. Eating more does not make us fat. Getting fat makes us eat more. Overeating was not a personal choice. It is a hormonally driven behavior—a natural consequence of increased hunger hormones. The question, then, is what makes us fat in the first place. In other words, why is the body set weight so high?