When we eat a lot of carbs, the body releases insulin - does that matter? Actually it does, because once the body's glycogen stores are filled (they are located in the liver and the muscles), any excess carbohydrates are converted into fat and stored.
So even though carbohydrates themselves are fat-free, excess carbohydrates end up as fat!
So any meal or snack high in carbs will generate a rapid rise in blood glucose, followed shortly by a rapid rise in insulin into the bloodstream. Insulin then lowers the levels of blood glucose.
Now remember, the job of insulin is to store excess carbs in the form of fat. So the insulin that's stimulated by excess carbs aggressively promotes the accumulation of body fat. In other words, when we eat too much carbohydrate, we're essentially sending a hormonal message to the body that says "Store fat."
But it gets worse. Not only do increased insulin levels tell the body to store carbs as fat, they also tell it not to release any stored fat. This makes it impossible for you to use your own stored body fat for energy. So the excess carbohydrates in your diet not only make you fat, they make sure you stay fat. It's a double whammy, and it can be lethal.