I assumed, naively, this may have something to do with gas/air. Anyone whose lived at elevation and at sea level has probably noticed how bags of chips are flat at sea level, and bursting at the seems at 5k feet. Could that effect make us feel more full?
No part of you has gas and is sealed like a bag of chips, and any stomach gas would quickly reset to a new altitude. Otherwise scuba diving would probably not work at all. Equalizing your inner ear to pressure changes, and possibly farting, is all it takes to reset your internal gas pressure to altitude changes.
