While the weight gain is a fairly common side effect of AI's, it may be in your best interest to see an endo dr IF thyroid problems run in your family OR if you gained the weight very quickly; such as 12 lbs in one or two months. If it's just been a steady gain since you started your AI meds, it's likely not a thyriod concern.
As everyone else has said, you just have to find that right balance. It's hard, I know. Like fighting an uphill battle.
It seems most of the meds I take are known for causing weight gain. I easily lost 90 lbs prior to cancer in 2005 - but now in menopause at 34 and taking these medications, I have gained 60 lbs in the last year. I have yet to talk with an endo doc but plan to as thyriod problems run in my family, even though cancer did not. I swear between the weight gain ,joint pain & hot flashes I sometimes wonder, but I don't want to worry about cancer coming back a 3rd time, as I've just been through it a 2nd time and recurrence is no fun. So I think I will take the weight gain any day cause at least I can TRY to control that!
Best of luck.
Angi