Hi Amyh
I’m new here today (just joined today) and told I also have Graves (I’m not convinced but that is a different story). Regardless- I AM hyper thyroid; I AM on Methimizole. I DID gain 30# over the last 2 years I have been sick with this (not diagnosed until recently). My endocrinologist ALSO told me this was impossible and that I would gain on the methimazole. It IS possible. I lost 8# in a little over 1 month on the methimazole with no change in diet/exercise.
Thyroid imbalance affects everyone differently. My endocrine surgeon said she has had a few (not many- but more than me) who GAINED when hyper- and not because of eating more. Easier said than done- but focus first on getting thyroid balanced- and then worry about the weight.
Lori