By adding weights, yr muscles will work harder so u will notice a bit difference in muscle size over some time. But dont expect to be muscular.... the difference will be sonething like between yr right and left hand. Its good for bones too.... makes it stronger...

Side effect.... its not too fun carrying weight around and may be bit tiring. Also not too great if u suddenly swing yr arm and catch a girl in the nose ....

Anyway, i think its quite alright. My professor of medicine walks around everyday treating patients with weight on her arms.