How can 15 yearsold lose weight fast? -

hi, im 15 years old and i weight nearly 70kgms (154pounds) and im 167cms (5.5 feet) high, i go to a gym, but a have a belly and i wanna get rid of it as soon as possible! i do leg raising sit-ups before i sleep everyday since nearly 1-2 week(s) how many should i do to lose my belly fast, plz help and thnx...

all other answers are advertisements well, do you jog?you shouldat least for half an hour every day(starting at a low)