Is energy expenditure actually greater at a higher altitude? Obviously physical exertion is more challenging due to lower oxygen concentration, but does that translate to increased caloric needs for the same activities? I'm originally a lowlander now living in the high Rockies at around 9000ft (been here for the last year and some). This is something I've been curious about lately as my appetite is clearly greater living here than it was at sea level.
Interesting observation, I've had the same experience when going in the mountains. The natives in the mountains usually say that the air increases your appetite.
The answer is that the basal metabolic rate increases between 6 and 28% http://jap.physiology.org/content/16/3/431.abstract
A lot of things change in your body at altitude. You even create more red blood cells. Your body is making all kinds of changes and compensations and this has to have an effect on energy expenditure even at rest. Until you acclimatize and it becomes your new normal.