They eat because they are fat they are not fat because they “over” eat. Once fatter, they must eat more to maintain energy levels.

Taubes makes much of the fact that some people – probably for reasons of genetics – tend to fatten more easily than others, even if they eat the same meals. Without it, the insulin signals hunger in its search for more glucose. Just as blood sugar requires insulin, so does insulin require blood sugar. “The more carbohydrates we eat, and the easier they are to digest and the sweeter they are, the more insulin we will secrete, meaning that the level of it in our bloodstream is greater and so is the fat we retain in our fat cells.” (WWGF, p.10) The kicker in this situation is that the more insulin in our veins, the hungrier we feel and the more likely we then are to go back for a second piece of cake, or to want lunch early, or to suffer a snack attack. Now back to the all-important insulin, which the pancreas produces primarily in response to carbohydrates. Bread, on the other hand, is nearly 50% carbohydrate by weight. An apple, though, is only about 10-12% carbohydrate by weight, most of it being water. It also includes our everyday fruit and vegetables. The universe of ‘carbs’ therefore includes more than starchy vegetables (potatoes) and grains (wheat, rice). Milk also provides sugar in the form of lactose. These sugars in our diets come mostly from plants in the form of sugar, starch, and fiber. Scientists call them saccharides because they are essentially sugars. What is a carbohydrate? Before going further, it’s important to remember what a carbohydrate is. He quotes one Harvard professor this way:

Among insulin’s several roles are those that contribute to adiposity: the regulation of blood sugar and the storage of fat. Taubes explains clearly how carbohydrates are “uniquely fattening.” Why? Because of insulin, that enzyme made famous by diabetes.

The biggest surprise was that some calories are more fattening than other calories – surprising because we have been hearing statements like “a calorie is a calorie” as if all were treated equally in the body. The author was surprised by some of what he uncovered in his search.

Why we get fat