Robert Lustig argues insulin is required for weight gain, pointing to type 1 diabetes patients who lose weight without it. He claims high-glycemic carbs, especially sugar, spike insulin, making food quality matter more than calories.
Chapters
There is no fat gain, there is no weight gain without insulin. Insulin is essential, and we know this because all you have to do is look at type 1 diabetics and how much weight they lose and how much fat they lose because there's no insulin to push on the adipose tissue in order to get it to increase its size. And that is also true. So the goal is keep your insulin down. Well, what makes insulin go up? High glycemic index, carbohydrates, and in particular, sugar. So this says that it's not how much you eat, but rather what you eat, that it's not the quantity of food, it's the quality of the food that matters, and that insulin is the primary driver of fat cell storage and also cell division. And those things are true. The question is, is the model true? Again, all models are wrong. Some are useful. How useful is the carbohydrate insulin model.