That’s a tricky question because each of us can only write from our own experience. Every case is different. I was pretty overweight when I first started exhibiting Graves’ symptoms, and I lost 75 lbs before I was diagnosed. I was down to my high school weight, but looked weak and sickly (largely due to loose skin and lost muscle mass). After I started treatment (methimazole), I gradually started regaining the weight I’d lost, but at my age (late 40’s at the time), more of the weight ended up around my middle. Also, since I’d lost so much muscle, my body composition shifted (higher percentage of fat vs muscle) and I think that caused me to gain a few extra pounds on top of those I’d lost.
I’ve recently started to lose a bit of weight, though. I’m down to my pre-Graves’ weight again, and hopeful that I can keep going.
As for whether or not weight gain is inevitable, I would say, not for everyone – at least not beyond weight lost due to Graves’. Weight gain is a common complaint, but I do know Graves’ patients who still look great. They just don’t often post on bulletin boards.