sugar!! That is what I found out! I stopped drinkin soda and eating alot of sugar!

i advise you to drink green tea 1-3 glasses per day is enough for you're age.. green tea speeds up your metabolism
drink lots and lots of water 8 glasses each day.
do not snack
do not eat 6 meals a day, try to only eat 3
if you are really hungry and you've had all your daily meals snack on fruits ( oranges, apples, bananas )
exercise more try and run for at least 30 minutes a day
get more active eg: instead of asking your mom to pass you the remote control get it your self it does count as extra exercise
get more sleep it prepares your body
stretch, yes it works and it doesn't just help you lose weight it helps with you're growing to make you a little taller
count your calories try to stay under the amount of 1000 calories per day
change you're lifestyle it makes a difference
do not eat candy or chips eat more greens or protein bars
avoid fast food and cut out fried food tell you're mom when she cooks you're meal to oven cook you're food do not fry it
chew gum because when you chew gum you do not pick at food for example if theres some chips in you're cupboard you go to them a think good damn they look good then you would say no i cant pick at them because i dont wanna throw my gum away
do not eat after 6pm because before 6pm you can burn all you're food off and if you eat after six it will lay on you're stomach as you eat.
do not eat before you go to sleep
drink a glass of water before you go to sleep
drink plain hot kettle water because it speeds up you're metabolism
do not weigh you're self everyday because it torments you,weight you're self once a week ( every Monday )
good luck! avoid wheat, pasta and stuff with alout of calories like mayo, ranch!

ramen noodles and tomado soup and soy beans

avoid sugar, excessive sodium, flour ( pasta, breads, rice), carrots, potatoes, peas and corn. drink 8 glasses of water a day. eat lentils and soups. you'll be fit before you know it.
good luck!!