While you are having radiotherapy, you should try to make sure your weight (and fat/muscle ratio) doesn't change between the planning scan and the end of the radiotherapy. That's much more important than dieting during those weeks - you want your internal organs to stay in the same place. You may have to change your diet to a low fibre one if the RT gives you excessive diarrhea, or for a very few people, you may need to add fibre if it makes you constipated.
One guy going through it with me was told to go and eat some more cakes, because he was losing weight (particularly visceral fat, I suspect), and it was getting harder to align the treatment zone to his prostate.
My RT sessions were at lunchtime and I missed lunch everyday, without really noticing any extra hunger. This would probably have put me on a weight-loss trajectory, but I was weighing myself every morning when I got up, and adjusted my other meal sizes to keep my weight constant. I also kept up my exercise (mainly cycling) throughout. (I was actually trying to maintain my body composition, not just my weight.)
Edited by member 09 Apr 2020 at 05:16
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