I am pretty thin and yes could be in the perimenopause too.
The fat does not seem to go on
first though not these days, it goes on
my legs and tummy, but then i dont like to get too big so keep slim, or try to. size 8, 5ft 2".
so lifting weights would make your arms better, the thing is i am not sure of this, as actually i think i do lift a lot of the time anyway, heavy shopping and do care work, ,a few hours each week and that uses your arms a lot really, day to day thing.