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

by Jason Fung

INSULIN I CAN MAKE YOU FAT ACTUALLY, I CAN make anybody fat. How? By prescribing insulin. It won’t matter that you have willpower, or that you exercise. It won’t matter what you choose to eat. You will get fat. It’s simply a matter of enough insulin and enough time. High insulin secretion has long been associated with obesity:1 obese people secrete much higher levels of insulin than do those of normal weight. Also, in lean subjects, insulin levels quickly return to baseline after a meal, but in the obese, these levels remain elevated. Insulin levels are almost 20 percent higher in obese subjects,2 and these elevated levels are strongly correlated to important indices such as waist circumference and waist/hip ratio. The close association between insulin levels and obesity certainly suggests—but does not prove—the causal nature of this relationship. Insulin levels can be difficult to measure since levels fluctuate widely throughout the day in response to food. It is possible to measure an “average” level, but doing so requires multiple measurements throughout the day. Fasting insulin levels (measured after an overnight fast) are a simpler, one-step measurement. Sure enough, research reveals a close association between high fasting insulin levels and obesity, and this relationship becomes even stronger when we consider only a person’s fat mass rather than his or her total weight. In the San Antonio Heart Study,3 high fasting insulin was tightly correlated to weight gain over ...