I've been thinking about this a lot lately. A few weeks into treatment I noticed I had gained a little belly even though my weight was the same as when I started. My arms and legs most notably have lost muscle.

Last week when I went for a very short run my legs were completely worn out. After less than two miles. Before starting treatment I had run a 10k. So in a span of 6 weeks I've gotten completely out of shape.

I'm no expert on diet/metabolism, but I have lost muscle and added fat. Kind of an anti fitness program. Maybe the reduced activity and greater calorie demand from cancer treatment drives this. Or maybe a side effect of the treatment itself.