I know for a fact that losing weight can be problematic. I never, ever had to diet until I hit my 30's. Never. I did go through a super-skinny (anorexic) phase in my mid-teens, but I snapped out of it within months and never did anything so stupid again. I wore an average size (9/10 juniors) until I had Tori, and I actually got pretty close to that size again after with a bit of work. Well, when I hit around 38 it started to creep up on me, and my sisters as well. Quitting smoking, while a definite plus, also zapped my metabolism and now I'm learning the hard way how weird our systems can become with as we age.
I work just as hard as ever, eat far less than before, and yet I just can't seem to lose anything. My doc says it's just part of getting older, but at the same time tells me that losing 15-20 pounds would be a healthy thing to do. (Yes, I want to choke her when she says that- the last time I said perhaps a little nicotine would rev up my metabolism, and she quickly backpedaled on the preaching). I don't eat sugar, I eat very little bread or fried foods, and I know I seldom exceed 1500 calories a day. I have just become resigned to doing the best I can for as long as I can, and so long as I am doing that nothing anyone says is really going to get to me. (Now, I just have to stop getting on myself....).