Hi, new poster here:
I’m a distance runner. By the time I was diagnosed and had commenced treatment, I had lost about fifteen pounds of muscle mass, along with all of my fitness. I had trouble climbing stairs or carrying anything that weighed more than my purse. I looked terrible, too.
I got up to 40mg/day of methimazole. The endo I was seeing overmedicated me and misread my bloodwork, and actually tried to up my dose to 50mg when I already had gone hypo. The result was like being fired out of a cannon into a brick wall. I gained weight as rapidly as I had lost it (2-3 lb./week), despite consuming at most 800 calories/day.
I would say that once I had stabilized it took me a year of hard work (strength training, running 40-50 miles/week) to get back to where I was, rebuilding lost muscle mass and losing the fat I acquired when I went hypo. I’ve never lost weight easily — I’m terrible at dieting. So, we’re talking about 10-12 pounds of added fat, and it took me a year to lose most of it.
I think that, in general, if you go hypo your metabolism will slow, so if you do not adjust your habits you can expect to see weight gain. But like others already have noted, some people gain weight when hyper, and some do everything they’re supposed to do but the weight will not come off. I agree that at any rate your first goal should be to stabilize
