63kg doesn't seem very heavy...is the loose weight idea based on any testing/ body fat percentages etc or just an idea
I have been lighter before ~60kg in uni (yet am stronger than then). There are rough guesses from fat percentages and height but they have quite a large range going as low as about 58 up to 65. The main motivation is that I have never tried to diet and eat better.
So it is as much as an experiment than anything else.