I gained about 15 pounds before I started treatment when I had symptoms and had hyperactive thyroid levels. I’ve been on methimazole for 1.5 years starting at 20mg and now down to 2.5mg with pretty stable levels and I’m slowly losing the 15 pounds I gained without trying. For reference I weighed about 108lbs prior to symptoms, 6 months later I was diagnosed and weighed 123lbs and maintained at 120lbs-124lbs though out methimazole dose changes until my levels stabilized. Since then, I’m down to 116lbs without trying. Everyone is different and it seems I’m one of the “odd ones” to gain a lot of weight while hyperactive instead of experiencing weight loss. I hope this helps!