| First you need to burn that fat, even if you do 1000 sit-ups you won't get any result
Sit-ups, Crunches, Leg lifts etc just give you strenght it won't burn the fat on your stomach. You should run pretty Much or Get a station Bicycle and train on that
Try eat Health you know what they say : you are what you are eating
A tips for you when you train the stomach
Don't do 1 kind of exercise cause that won't train the whole body
Do V-ups and Leg lifts for the lower part, Sit-ups and crunches for the upper part
and Oblique Crunch (elbow to Knee) to train the oblique | 
