What is the fastest and most effective way to have flat stomach ?

Burn fat: Fat burning exercises, that help you to lose midgut fat is the best way. This means cardiovascular aerobic exercise as tolerated. If you burn fat by increasing your calorie expenditure through exercise, you will lose midgut fat and tone up other areas as well. Walking is free, and easy to do. You can start a walking program most days of the week and increase the amount of time you do it.

^ exercise v weight: For a flat abdomen eat healthfully ; be physically active. Calories burned must > calories consumed. To tighten ab's do crunches, reverse crunches, exercise ball crunches, pelvic thrusts, lying leg raises, side bridge ; “bicycling” exercise on your back. Engage in regular aerobic exercise (i.e., running, swimming, nordic track, bicycling, kickboxing, walking, cross country skiing, hiking, etc.).