How come I'm lighter then when I was younger if I eat more and I'm less active?

Anonymous
When I was younger I used to eat a normal amount of food (900-2000 calories a day) and exercised for a 1/2 hour every day and I was fat, not muscular. At age 12, I stopped eating for 1 1/2 months and lost 80 lbs. at 13 I started eating a lot and gained 20 lbs. I just kept eating more and more. Now, two years later, I eat like a pig (between 1800-5000 calories a day) and never work out and I'm 50 lbs lighter than when I was a kid with 14% body fat. So how come at age 11 I weighed 160 lbs at 4 foot 9" and ate normaly, when at age 15 I am 5 foot 1 3/4" and weigh 110 lbs and I eat a shit load? How come this happened?
How come I'm lighter then when I was younger if I eat more and I'm less active?
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