I have thought about putting on a bit of weight to help my breast growth, but I don't think I will. Not that I don't need the help: I just about cried when I didn't come close to filling an AA. But, on the whole, I am happy at the weight I am (150-ish lbs).
I like the fact that I almost have a figure. I am getting a little bit of curvature in the hips and, if I remember to suck my gut in, my shape looks all right. I wouldn't want to jeopardize all that by having weight go back in the wrong places. Besides, I have spent a bundle on replacing my entire wardrobe. I wouldn't want to have to start over at a larger size.
My boobs may be little, but they are really cute. They are growing (slowly!) so maybe I'll get up to a numbered size one of these days. In the meantime, a padded bra does the job.