Hi and welcome, as has been said everyone is different.
I am 1 week post op and as yet have not 'dumped', my energy levels are slowly building and although my children are now adults i couldnt see me lifting one for a while.
I was advised to have 3 protien shakes a day plus to take the calcium and multivits + minerals in chewable form - Bassetts active health was recommended from the start, and i actually started them a month beforehand to help build me up prior to the op.
As for hair loss its too early for me to know about that yet, however i understand that all those who lose a lot of weight have some but that its never really noticable, just a thinning in keeping with the slimmer you