In reply to Sean Flynn:
eat what you can.
altitude sucks your appetite away and cam make you feel queezy, so anything that goes down is good. the best thing about expedition meals is they come in a handy ziplok packet so when you throw the whole lot back up again you can seal it nicely.
fat metabolizes less efficiently up high, but that said, i personally crave it up there.
you also want food with a high water content to replenish fluid from fluid loss.
depends too where you are: a high basecamp, actually climbing, in a tent on a ledge way up.
you want a strategy that covers the lot.
at BC youll be acclimated better so can load on the calories you need. for that take as wide a range of food as possible.
whilst youre climbing things like bars, gels etc work as they are simple to get at.
stuck in a high camp or bivvy is a whole other world and hard to pick until you get there.
across the spectrum, th worlds highest peaks have been with anything from dozens of gels, slabs of pig fat, jars of peanut butter, muesli, instant noodles, sausages and morroccan lamb couscous.