I'm more than a gaijin, so much more.
When I came to Japan, I was just shy of 6ft tall, fit and 180lbs. One of my first students, a doctor, said he was concerned, because I was "fat". Then, what with the different foods, and the fact that we tended to drink our dinners (beer and whiskey vending machines on every corner, remember?), I dropped 10lbs in the first 3 months. My student the doctor said he was worried about me, I was too thin. Can't friggin' win with this guy...
That is to say, I'm fat. I used to be built like William Shatner in the original "Star Trek"; now I'm built like William Shatner in "Boston Legal". I super-sized myself. Sumo, minus the muscle... I'm still just shy of 6' tall, though.
No excuses. I've been lazy, haven't eaten well (or have eaten too well). My wife popped out 4 kids and lost the baby weight every time. I didn't. Gotta tell you, I would have gladly tried breastfeeding if it would have helped.
Other than the obvious health and aesthetic issues of being overweight, you'd be surprised at some of the things that arise. I said arise, not rise, Dirty Mind, and not that thing, either, thank you very much.
1) Good fucking luck finding clothes. I had real problems finding XXL shirts and jackets before (4L in Japanese size). Now? Forget it!
Oh... so much Japanese...