Are you a fan of the slogan "nothing tastes as good as skinny feels"?
I'm a slim 5'1 female and am still the same weight as I was when I was 13.
Do plenty of excise, drink lots of water, home-cook your meals, restrict your portion sizes and calorie intake.
Limit your quantities of refined sugar, bread, dairy, gluten and greasy takeaways.
Take up swimming, jogging and lots of walking.
Eat lots of nuts, pulses and raw veg.