No, doing sit-ups will not help you eliminate the fat that stores itself near your abdominals. But they are affective in improving one's posture or developing muscle tone in the area. As a personal trainer, I was always asked the most effective way to work your abs. The answer? It?' not too exciting; really it is just your basic crunch. The problem is that most individuals don't perform the basic crunch correctly, and end up developing their hip flexors instead. To do them more efficiently, you need to pick your feet up off the ground, and with your knees still bent, create a 90 degree angle in your hips. This helps take the hip flexors out of the exercise and isolate the rectus abdominus (the six-pack muscles). Also, short crunches need to be done, curling from the abs, and being sure to not flex your neck forward. If you put your hands on your head, keep your elbows out! Don't toss them forward trying to gain momentum. This is the best way to isolate your abdominals!