While I was in Japan, I ate both Japanese food and other, unhealthy snack foods. However, I wasn't nearly as hungry there. I ate about 2.5 meals a day, and was definately full all the time. My body breathed in the thin, and I was not hungry.
Now that I am home, all I want to do is eat. The fat air has gotten to me! I just eat and eat and never find myself full. It's insane!
My conclusion is, therefore, the air makes America fat ^_~