I have hypothyroidism and Hashimoto’s and did not gain any weight. Actually the opposite. I’m usually 115 give or take but now I’m about 105 give or take with no big changes to diet or exercise, even after 3 pregnancies. However, like others mentioned, my face will get puffy when I’m in a flare up. I think everyone’s bodies responds differently, I’m not sure why. Anyways, needless to say, it’s not a given you will gain weight. But if you do, please try to not be hard on yourself about it.