Here is my theory of the day. Our current lifestyle is very eskimo like. We hang out in our air conditioned igloos in the desert and generally don't get very much exercise. Eskimoes don't get much because they'll get eaten by Polar Bears or freeze. They have sled dogs, we have cars. We humans are pretty smart animals so we've figured out how to make seal soup up there without much competition from other animals. My point? They have already adapted to an environment similar to ours that we're just becoming acclimated too. We'll all evolve into short, eskimo like people in a few thousand years. Being tall may be attractive to women but my 6'5'' friend is constantly banging his head on doorways and other lowhanging obstacles. As the concussions mount his ability to impress women with witty pick up lines rapidly declines to the point where us average height guys can compete.
Here is the quote by Peter de Jager that sums it up "Any technology which creates abundance poses problems for any process which existed to benefit from scarcity."
If you look at that quote from a biological perspective, the process which exited to benefit from scarcity is our entire digestive system. We're going to be fat AND hungry people for a long time to come.