As you exercise, you consume energy measured in calories. When you consume enough to deplete the available energy, and enough to reduce the sugars that convert easily, the body goes after stored energy. That stored energy is largely in the form of fat deposits in adipose tissue.

But that process takes place non-selectively. You don't get to choose which fat deposits the body converts. That means, you can't 'spot reduce' by working on your abs. The effect is still achievable, but doing abdominal exercises alone doesn't target that fat.

When you focus on the abs, you will build strength in that area, by increasing the muscle mass in those muscles. That's helpful for a number of reasons. It keeps a firm, strong layer of muscle, which helps keep the stomach, and other internal organs well inside the plane defined by your hips. You get a nice trim, flat look.

Abdominal exercises help in another way, too. Since the abdominals are large muscles, they consume a proportionately larger percentage of energy than, say, your jaw muscles. That means that as you work them, they have to be supplied with more energy to move through the range of the exercise. That burns many calories, resulting in weight loss and fat reduction.

There is no gadget, supplement or drug currently on the market that will do that safely and effectively as a substitute. It can only be done through proper diet and regular, moderate to heavy exercise. There's no shortcut to a trim waist, at least not yet.

The effect is also limited by genetics and age. Some people store more fat around the middle more readily than others. Gender, obviously, makes a difference as well.

Many women in their 40s will naturally develop a pouch in the lower abdomen as their hormones change. Many men will naturally develop 'love handles' at the side, since they store fat in adipose tissue there more readily in their 40s than they did in their 20s.

In order to achieve the desired effect you have to approach muscle fatigue. There's no need to perform a hundred crunches to accomplish that. Done correctly, 20 reps are enough. You don't even have to go to the gym. You can do pelvic tilts while sitting in a chair in the office.

But for best effect, warm up and try the following:

Lie on your back, with your knees raised and cross your arms across your chest. Then lift your shoulders off the floor and hold for 30 seconds. You can feel the effect on your abs already. To make the exercise more difficult, put your hands at the side of your head. Don't use your hands to lift your head, just keep them still. For maximum effort, put your hands above your head, and then perform the same shoulder lift and hold, focusing on the abs.

Feel the burn. Repeat daily for 10 minutes or twenty reps. In a few weeks, you'll see definite results.