Also worth mentioning, if you go to Japan they don't expect foreigners to have the same body shape, height or width wise.
When I went over last, as a tourist so it will be different from living and working, but still perhaps relevant, I was a UK size 14 (5'7 and about 155lbs)
By Japan standards this would be huge, yet I didn't hear a single comment or see anyone stare and even found some clothes to fit (an XL woman's long sleeve blouse and size M souvenir type t-shirts)
I tried on a top in a boutique in shibuya and it was only a tiny bit too small (my boobs got squished) and the shop assistant was polite and helpful and seemed a little shocked when I said the top was too small (probably just being polite but still)

So don't worry too much!

Damnit, Jim, I'm a forum member, not a doctor!

I put your height and weight into a body mass index calculator and it says that your are under weight.

* Underweight = <18.5
* Normal weight = 18.5-24.9
* Overweight = 25-29.9
* Obesity = BMI of 30 or greater

You can put on another 10 pounds and still be classed as under weight. As far as I the BMI system is universal and not just used in Japan.

From experience
 

Hi--It's funny --your stats are like mine--not all gaijin are a lot bigger....I'm a small girl (damn welsh blood) and I'm 5'1 and about 101-102 pounds....
I find clothes in Japan really really easily and can fit in size s..I LOVE shopping in Japan...It's about a million times better than shopping at home.
You are gonna be A-OK...
Since I first moved to Japan in 2000 I have noticed that girls seem to have "filled out" more---it's a bit more fashionable to be a bit bigger (maybe Ueno Juri type size...not BIG at all just normal)..in 2000 the style was a lot more bone-like.
In any case I think any size is fine as long as you have confidence and style...I feel like the foreign girls who feel negative reactions might find those reactions are based more on a too-casual not fashionable, rumpled clothing style rather than body size. Just a few people here and there I mean. If I hear my Japanese friends or husband makes negative comments about larger foreign girls (verrry rarely) it's always cause the clothes are kind of....hmmm.....not because of weight.

You were very rude to MM no manners whatsoever.

read the date, this thread almost a full year old. OP hasn't been here in ages~

ahhh...if only OP was still here. then MMM would have to blush if he counts as rude here after what i'm going to write...thou not much point. still - maybe chance to revive this topic.
1. how dumb the OP has to be to not be able to find these statistics? seriously? it's just whole new level of lazy and stupid.
2. original idea is kind of retarded also. everywhere standards for beauty are the same nowadays. be pretty. it's all about proportions - you can be tall and sex, and you can be short and sexy. no one is going to tell to a hot girl that she is fat just because her "wannabe prefect" number is off.
i think this obsession some people have with numbers is BS. " oh noes..im 5.7 and 120 not 110" aaah! i can't imagine why would anyone care about the actual numbers if the person is pretty? i wouldn't care if scales showed by gf is 220 pounds as long as all is pretty and proportionate.
only worry about numbers in following cases. when you are under 80 and when you are above 300. unless you are a body builder.

oh thanks for that Columbine I had not noticed.