I Am 5 Ft 2 Inches And 45 Years Old And Very Small Frame, What Should I Weigh?

I would say nothing less than 50kg if you don't want to look too thin, to about 56kg, but remember muscle weighs more than fat so you could way a bit more and still look slim and toned if the weight is from muscle. I'm 5ft 2, very petit and small framed, uk size 6-8 and I currently weigh around 52kg. At my biggest I got up to about 60kg and lost the weight eating a calorie controlled diet and doing pilates. Once you understand the relationship between food, energy and fat its not very difficult to spot why you put on weight and how to manage it.