Sorry to mention this, but who concentrates on food digesting anyway? Food digestion is caused by a mixture of emulsifying, enzyme concentrated, acidic/alkali juices. These along with absorption of broken down food in the ileum (small intestine) will exert minimum energy/brainpower from any part of the body. Perhaps one could argue that the conversion of glucose into glycogen using the hormone insulin would require a small amount of brain power to release the hormone (after eating high energy foods). But it would require no more energy/brainpower than than the conversion of glycogen in glucose using glucagon (used if you didn't eat anything).

The only thing that could keep you up after eating (high energy foods), would be the increase in energy you would receive from the food, making you too energetic to sleep. But that would be about it...

Sorry for being a bit technical !