lol,over the years, i have spent time in the Alps- not too sure about, if the air has helped me anything.lol- Although, i do have to admit that the majority of people there are very thin and fit, indeed.(And i am i think a size 16 - i don't know-and i could hardly fit into the largest size there - but then again there are a lot of petite Italians) But, you also do a lot of things that involve movement there, like cycling long stretches, hiking, climbing the mountains, skiing, sledging.....like a lot of outdoor activities...and in London, i don't do any of these.lol
Well, I went to the Indian side of the Himalayas last summer and I can honestly say, I don't recall seeing a single overweight person.
Not only that, but I saw a lot of elderly people carrying huge bundles up very steep inclines without breaking a sweat, whereas I would be struggling after a very short time (without carrying anything!).
I guess there must be something about that mountain air that is good for you.