I think it would be worth considering that feeling good would better than looking good, if the worst possible scenario were to happen and you gained weight permanently.
From my own experience, I have gone from 57kg to 96kg in 8 months. The fastest gain was the first two, where I went from 57 to 82kg. Thing is, when you have debilitating health symptoms, what is the point in looking “sexy” if you can’t even enjoy every day living? Even if you don’t currently have any deblitating symptoms, they might be on the way if you continue to starve yourself (which is essentially what anyone who diets does).
I think the chances are very high that if you stick with it and stick with it well, you will find that the weight gain is not permanent. Actually, forget weight – what matters is how you look visually. You can have two people with identical weights, and one can look fat while the other looks slim or muscular. I think that it’s very likely you will find yourself with a decent looking body at the end of it all. I don’t think it’s ever going to be super-model skinny, though, but who wants that?
For your information, I am 182cm tall and male. The weight gain I’ve got I am actually pretty damn happy about. Some of the weight has been redistributed to other parts of my body and I can see that as time goes by, I’ll probably have quite a muscular physique. I’m not even doing any physical activities either! Just sitting on my ass all day playing video games.