A friend of mine used to practice Kapal Bhati everyday for 10 mins and she had lovely glowing skin. Also even when she put on weight, her stomach always looked toned. She never put on even a bit in her stomach area even when she had gained almost 25 pounds. Her father who is 65 years old also does yoga daily and he is extremely fit and looks like he is 10 years younger. So Kapal Bhati is a very effective way of getting flat and toned abs and looking young.
Initially you should start by doing it only for 1-2 mins because one might feel dizzy or nauseous, but with daily practice you will get used to it. Please find the link attached to get an idea about it: http://www.youtube.com/watch?v=1y3ZOCXEX98