"Hey, how are you?
I have something to ask?
It is a personal question, so forgive me if it feels rude.
That isn't my intention.
Any way here is goes.
I noticed that you have gained some weight since I met you.
Now this is not an issue if you are ok with that, but for some reason I feel like you are uncomfortable with it.
Just a gut feeling.
I just noticed over time.
Never had the opportunity before to have a conversation with you about it when I felt strongly that I should.
The question is just this;
Are you ok? Does it bother you?"