I am 5ft 2 and hover between 50 and 52kg. Any heavier and I start to feel Blergh. I am one of the lucky ones with one of those metabolisms. At one stage during a particular stressful time I weighed 45kg, I just could not get weight on and I was very self conscious and dressed to disguise it.

I am finding as I reach 40 and beyond I have to be much more careful.
I tend not to go by scales. I go by clothes size and how my clothes fit as to how I am going.