I used to be the opposite. I over-ate throughout my teens, to the level of consuming entire multipacks of chocolate and crisps every day, and hiding them around my room with the hope that nobody would find them. I was too lazy - and probably too embarrassed - to take them to the bin when I was finished. I hid the empty wrappers behind my wardrobe, under my bed, behind my cabinets, in nooks and crannies all over the place. I used to keep tubs of things underneath my bed to eat when I was bored (which was essentially all the time). I did literally no exercise, had very few friends, and became continually more and more depressed, which made me consume more. At school I used to eat at least 2 or 3 sausage and bacon sandwiches every day in between classes, and had a highly calorific dinner when I got home. I also drank about 6-9 cans of full fat fizzy drinks every day. I certainly exceeded 16 stone (224lbs), with a 40'' waist, at 5'7'' height.
When I was about 16 and a half, I decided to change course on this, and began walking 2 miles every single day, and attending the gym twice a week. I radically altered my diet too, and lost over 3 stones in 3 months. Over the last 4 years I've progressed and progressed, and now I'm 20 years old, 6 foot and 13 stone (182lbs), with a 34'' waist. I go to the gym every other day, play a lot of sport, and go running on a regular basis.
I still have the stretch marks to remember it by.