Hello, when you eat some carbs, your body deals with the blood glucose by using insulin. Insulin brings the glucose to the cells so they can burn it for energy right away. In the mean time, what happens to the eaten fat ? You can guess: straight to the storage because insulin inhibits lipolysis (break down of stored fat into free fatty acid readily available - it does not mean by the way that the FFAs are all used but they are available when insulin is low). It does not take much insulin for that to happen and it is completely normal. So while you digest your carbs, fat stores are not exactly in use and the extra fat that you are eating cannot be used either, so it is stored or crapped.