First, as a reassurance, its only temporary!
For those that did lose some hair (which is mostly everyone...though there are a lucky few that don’t) it all came back eventually. I have yet to read from anyone who is far out from surgery that it is permanent.
I started losing mine at 3 months, and it stopped around 7 months. I don’t know if it was because of time elapsed, or because I was done with rapid weight loss phase, though.
I am 2+ years out now and its ALL back (sometimes i think its actually thicker these days, but it might just be because of my hairstyle, lol).
I did cut it all off at the first sign of loss, and my hair today is no where near how long it was pre-surgery, but thats just a matter of time (though I dunno if I even want to grow it back to that length anyway.)
I don’t have any tips to prevent it, honestly I don’t really think you can, but I’m sure others will weigh in on this subject.
Good Luck!
P.S. despite the current hair loss, are you satisfied with your WEIGHT loss so far?