not sure at 18 years old but 15 years old I was 15stone 2 (did project at school were we had to record height and weight on board at front of school and remember it to this day) and at 19 and meeting my husband i was 18 and a half stone..
I was 11 stone 2 lbs (and 5ft 5in). I know exactly cos we had to write our weight on the application / health info for uni and I was embarressed cos it sounded like loads (although I think - looking back at photos - that I looked good!)
I always looked like I weighed less tho. Wish I weighed that now!!
Not sure, but that was the time my weight got out of hand, because I had left home, and had freedom, and felt alone too.
What i do know is, Iam less than I was then, and probably the smallest i have ever been in my adult life and really does take some getting used to.