Can you tell me your weight?
You should not do dieting b/c this is your growing age you need all ingredients of food.
What you do increase your activity. Join a game club, walk or play at home as well.
Do house hold work as well.
In food do not take sweets, potato, cola drinks. Junk food & chocolates.
Rest of every thing you can eat.
Drink more water than before.
Never take any thing in between the two meals.
Then please let me know.