Doot-I have been on Tamoxifen just over a year and have put on 3kgs. Depressing when I eat well and go to the gym. From what I've read it seems that as you get older you just have to eat less and exercise more as our metabolisms slow down. We don't need as much food. This plus Tamoxifen doesn't help! Tamoxifen also stops oestrogen reaching our cells, so our body tries hard to hold on to fat reserves as oestrogen is also stored there. I blame this too. You have the right attitude. Stay informed so you can make the right choices. Your GP will guide. Cheers!