With the chemo I lost weight it was the on going treatment, Femara that piled it on. Tamoxifen has the same result in lots of people.
My girlfriend, who has just finished chemo put weight on as all she wanted to do was eat all the wrong things on the other hand I just wanted things like broccoli, oranges, cauliflower, chicken breast.
I put on but doc said it was a good thing (most people on the regime I had lost weight) - plus I was on steroids for anti sickness.
TBH - I didn't care about the weight at the time. Just concentrate on looking after yourself and enjoying yourself. Once you're back to full health you can tackle any weight gain
My tips are sea-sickness bands (queeziness), ice pops and pineapple (sore mouth). Oh - and try to laugh until you nearly pee in your pants at least once a day - it does you the world of good at the best of times