/e
Let me explain it a bit more in depth.
When you are eating a sandwich, the carbohydrates from the bread will act as the main form of energy, then the proteins and finally the lipids (very general view). If you were to eat a whole bunch of sandwiches, you would need to exercise for a very long time in order to be able to reach and burn the fat taken from them, however, if you are to ear a single sandwich, you would not need as much exercise, it would be easier to reach to these lipids and get rid of them while building on with the other resources.
Not only that, but it is also a lot more beneficial for your body to receive smaller amounts of food during the day rather than a huge amount of food all at once.