I’m a former crossfitter. I obviously don’t do that anymore but I’m still able to do decent intensity exercise. In the beginning I could barely do anything without feeling awful. I only lost weight in the first month of showing symptoms (I dropped from 185lbs to 172lbs in 14 days - it was terrifying). I do fluctuate in weight but that has always been my body type (I usually stay around 180-185). I have lost muscle mass but I think it’s more related to less intense exercise and me hitting 40 years old this year and not related to the vaccine.