Myomectomy should not affect weight in the long-term. The only effect would tend to be in the short-term because your activities are limited during the surgical recovery period which I believe is 6 to 8 weeks.
However, hysterectomy (removal of the uterus) does seem to be linked to weight gain (I have read about 25 lbs. the first year post-op). Even when the ovaries are left in place, compromised ovarian function or complete failure are common which is probably the cause of the weight gain. But even when ovaries continue to function, there may be some other mechanism for the weight gain.
The uterus, ovaries, and tubes work as a unit / system a woman's whole life. Although their reproductive capability ends at menopause, their post-menopausal functions take over and the ovaries continue to produce hormones into a woman's 80's. These are vital for optimal health.
This may be more than you wanted to know but just passing on the info. Hope it has been helpful!