On top of that, in Skyrim they're at a high elevation, which means thinner air, which means every action takes a lot more energy than normal and the body gets fatigued a lot faster than normal, which means it will rapidly burn off fat. And, considering the dynamic terrain, anyone who moves anywhere outside their own house is going to get a workout. They also don't eat fast food and the other garbage that contributes to obesity in today's world, so their nutritional habits themselves create a leaner populace. And, they don't sit around in front of computers and desks all day, there is always maintenance to be done to continue their mode of life, just as their is today by people who live within similar means. In those conditions, you live to work to live.
And fat people in the middle ages owned their own estates with servants enough that they had to do nothing. A single Skyrim town would be the number of people that would serve one such a fat person, ignoring the effects of the mountainous Skyrim environment.
Again, it'd be heavily unrealistic to have fat people in Skyrim.
So everyone in Skyrim is constantly moving to keep himself warm? Looking at some of the armors/clothes shown on the screenshots that would probably be needed...lol.
I think what you describe is your own vision of how Skyrim should be and not how it will be in the game (and not how I envision it to be either - a country full of tough guys/gals living off the land?). There is more than enough food, there will be wealthy people and no, not everyone will be having an exhausting job and walk around in the mountains constantly. Even in cold climates there were fat people in the middle ages.
No one is saying that 30% of the population in Skyrim should be fat. But there should be a few fat people, everything else is unrealistic in a country with enough food and wealth. Enough wealth to build large cities, castles etc. It's a bit ridiculous to claim there should be no fat people because everyone in Skyrim is a tough guy who's constantly working, fighting and running around in the mountains.
EDIT:
Oh and...