Passport?
I've lost 185lbs and have had no issues. Both with my passport at customs/immigration and with my license with TSA. I often get comments, but they are always very positive comments, they never actually question if it's me. If it makes you less nervous, and you can afford it, go for it. If not, I doubt you will have any issues.
I do have to say that my license expires this fall, and I'm pretty happy to be getting a new one, as I am ready to have the "new me" on my license. I have a few years left on my passport, and am just going to deal with it
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