Letrozole & weight gain

I've been on letrozole for four years without any weight gain. I was at my lowest weight since college when I started it and weigh the same now. Independently of breast cancer diagnosis, I spent the last decade or so increasing exercise and decreasing calories a very small amount at a time. Many people wouldn't find such a slow system rewarding and I'm not recommending it, but I can maintain it--and no effects from the letrozole. Wishing you the best with the aromatase inhibitors.

@mir123 Thank you for sharing your experience. I had very bad joint pain from anastrazole and had to move exemestane. Now with this weight gain, I want to try letrozole. I hope it doesn't bad joint pain.

@lesliek808 I wish you all the best with this. I gather there can be bad side effects with all of the aromatase inhibitors, but it is good to see if one works better for you. I've been very lucky with the letrozole--no side effects and I credit it with keeping the breast cancer at bay.

I gained 8 pounds in three weeks on Letrozole while on a 1200 cal 110 g protein diet.

@galesy Oh that's terrible. Not looking forward to starting this drug. After reading about bone thinning and high cholesterol (which I have already), I really have to weigh in on what's best for me. I've been so depressed (probably another side effect of the exemestane) too.

It's just not fair, is it? We have to take care of others (for me, it's my elderly mom and my retired husband), so I have to be around as long as possible.

Thank you for sharing.

@lesliek808

I had a lot of side effects. Mine were the less common ones for the most part, but I was completely miserable and the doctor took me off the pills to give me a break. But the doctor wants me to go back on a different AI. Frankly, I’m afraid. I see the doctor in a couple of weeks.

I didn’t have a problem on Anastrazole - able to maintain but not lose. When I went on exemestane, it was crazy. Starting the third month, suddenly gained 10# in a week with no other changes to diet or exercise. Of course mentioned it and was told it doesn’t cause weight gain, just a redistribution of fat and difficulty loosing weight. I was barely able to maintain at the increased weight on 1200 or less calories a day (not intentionally low, just what the post chemo appetite levels are). At 18 months because of other side effects, he told me to take a 4 week medication vacay, I took 6 because it took 4 weeks to feel good, lost 12 pounds. He wanted me to restart and the weight came back along with all the other problems. Finally now been on Letrozole for about 3 months and while still can’t lose (d**n menopause), at least I’m not seeing the increases. Still monitoring as it takes me 3-4 months to see side effects but so far, I’m doing better on this one.

Hello! I’ve been on Letrozole for almost a year and have not had a weight problem. I lost 30 pounds from the time I was diagnosed with bc (November, 2024) until I finished radiation (August 2025). I’ve gained 10 of that back (hello appetite, lol:) but don’t put that on the Letrozole. I haven’t been exercising as much as I did before my cancer diagnosis but am slowly getting back to my daily walks. I feel that when I get back to daily exercise I’ll probably lose a bit more weight. Before cancer I was exercising daily but also drinking most days too. I’m not drinking daily anymore and I think that’s been a big difference with my weight. With Letrozole I have a little joint pain but maybe no more than just menopause would cause. It’s not terrible and I feel better mentally taking the meds. Best of luck getting on the right one. 🙂

Also see related discussions:
- Do aromatase inhibitors (like anastrozole) cause weight gain?https://connect.mayoclinic.org/discussion/anastrazole-and-weight-gain/

- Has anyone lost weight on Lupron and Letrozole? https://connect.mayoclinic.org/discussion/has-anyone-lose-weight-on-lupron-and-letrozole/