Comment by qingcharles

I wonder about the same thing. I was a fat kid, but my best friend was so skinny. We would walk down town and he would stop several times to stuff chocolate bars in his mouth, and then buy two McDonald's meals. I would do none of this and our physical exercise was the same.

Then we went away to University and in his mid-20s the poor guy suddenly, almost overnight, put on a ton of weight.