the thing is more complex than it seems.
I'll give you an example: if you have a big belly and you focus your traning on belly, you will increase your belly!
This is because while training increase muscles only in the area you train (running-> legs and abdomen, f.e.), it decrease the fat equally over all the body.
The distribution of adipose tissue is random: girls have it mainly on breast and hips, man on belly. But things change from person to person.
If you want to decrease only the belly, my advice is to make a sport that uses most of muscles: aerobic gym, dance and swimming are good examples!
well thanks @cryptoitaly for the advice, i will play badminton..
Hope that will work for me ....