The reason wake and bakes simply work because there is a large amount of melatonin and seratonin (sleep hormone, and the 'feel good' hormone) left in your bloodstream that enhances the high.

THC is absorbed in the lungs, which then transfers directly to the bloodstream, and goes to your brain. The blood circulates through your entire body, and mingles slowly into your fat cells. That's it. The only contact it has with your stomach is on the outside, where veins surround it.

The only way a wake and bake session would matter if your stomach was full or not is if you baked brownies and ate them.