Hi Susan,
I've lost weight (only about 3 or 4kg), but I was pretty lean to begin with, and used to doing lots of exercise. I've been lucky in that I haven't had much nausea and have been able to keep up a pretty steady (moderate) exercise program. Plus, for the first month or so of treatment, I couldn't taste sugar, so sweet things tasted yuck. Then fatty things tasted like slime, so I chewed up a few more fat-stores just eating 'good' fresh food. Now my taste buds are kind of okay and I'm eating pretty much whatever, but trying to maintain frequent small portions rather than big stuffings. I've also noticed that the steroids you get with chemo make me hyperactive, so I just go with the flow and motor around while it lasts.
But (here she goes again) everyone is different. I think my chemo ride has been relatively smooth (touch wood, 2/8 to go) and I know lots who have not been so lucky, and just need to eat whatever they can, when they can, and who have to go without much in the way of exercise for the duration...
So: go with your own individual flow. If you gain weight you can always work at getting lean again when you're feeling okay; but if you're feeling okay, make the effort to move your body -- it eases fatigue (strange as that sounds) and helps you sleep and feel better. And in fact gentle/moderate exercise is positively correlated with bc survival. But don't beat yourself up: if you're up to it, you're up to it; if you're not, you're not.
I've totally NOT answered your question, but there you go!
hope your heart test goes well, and good luck on your chemo ride.
Go well,
Heather