My day oncology checked my weight at every treatment, and discussed with my oncologist my dose when I lost weight, but there was no suggestion I should not lose weight (I wasn't really trying anyway!) or that adjusting my dose (my oncologist didn't) was in any way difficult. If you have 6 months of chemo, and your pattern of eating and exercise changes, it's not hard to imagine that it will take much longer than 6 months to get back to a healthier pattern - weight is unhelpfully like that! . I was double lucky in that my pattern of eating changed (due to taste buds loss - I could taste healthier options, ate less, could not stand alcohol) and I didn't have any significant change in exercise as I did not have fatigue. So I wasn't trying to change back to my old pattern after chemo, just trying to keep to the new one.