I had a TT on 7/18 and as of yesterday weighed 5 lbs. less than I did the day of surgery despite eating like a fool and napping like... like napping's the only thing I know how to do besides eating.
NOT that I expect that kind of good luck to last. Trying to prod butt to gym right now. TT or no, eating lots and moving little will expand my horizons pretty quickly.
But I can say that the members of my survivors group are mostly average weight to thin, so a TT's not guaranteed to plump you up. None of them looks to qualify as "obese" and there are at least 25 people in the group.
i gained weight when i became hypo but after my tt i didnt gain weight i think it depends on wether you are already hypo or not