I think I will start exercise now.but I'm not sure about suitable age
You can lose weight at any age!
You can start at any age. Just wouldn't push to hard at first. Work your way up.
Agreed with the others, it's not age-dependent! You can totally exercise and lose weight at any age. If you are quite young or if you have any specific health concerns, you might want to talk to a doctor or other professional first, just to make sure that the diet and exercise plan you choose is right for you and will meet your body's needs.