I was my current height, 5 6 1/2. I weighed 119 pounds through HS and until I was about 28. I didn't think about what I ate - mostly healthy, balanced meals. When I was full, I couldn't eat another bite. Whether I was halfway through something or only had one more bite on my plate, I just left it there. If I had a packed lunch in HS, I'd eat two sandwiches, but lunch side dishes were limited - don't remember getting things like chips or cookies, just the two sandwiches and maybe an apple. And I'm sure the sandwiches were on white bread! We didn't eat between meals either, except plain white bread or vegetables (carrots, celery) - basically the kind of stuff you'd only eat if you really truly were hungry.
I knew I was thin and was happy to be thin. I seem to remember wearing a size 9 (how could that be?

), while my little sister apparantly wore an impossible to find 3 at the time. I do remember the summer after HS when skorts were in having a 9, a 7 and a 5 that all fit. When the Twiggy look was in, I looked like Twiggy, flat chest & all. I look back at pictures now and I feel I looked emaciated.