As others have said, it increases available calories and nutrition. It also makes sense, thermodynamically. You're using outside, normally unavailable energy (t

As others have said, it increases available calories and nutrition. It also makes sense, thermodynamically. You're using outside, normally unavailable energy (the fuel) to process your food so that you're not using the precious little energy you've managed to store in your body. It increases the total available energy to your body by indirectly supplementing with sources you normally couldn't.