You lose fat by burning more calories than you eat, so the best machines for flat abs are those that allow you to burn calories the fastest. As your body grows leaner, your stomach will flatten proportionally. Although no single winner exists, cardio machines are most effective at calorie burning -- the best option for you is the one that you enjoy enough to use regularly.
Top Calorie Burners
Running or jogging on the treadmill is one of the most efficient ways to burn calories, although walking on the treadmill is not nearly as effective. You can also burn calories quickly on the elliptical machine, stair stepper or stationary bike. The exact number of calories burned depends on your speed and resistance, but all of these options typically burn between 225 and 400 calories in 30 minutes for a 155-pound person. For every 3,500 more calories you burn than you eat, you lose about 1 pound of fat.