If you are an adolescent male and you have man boobs then it is most likely hormonal changes your body is going through. You will also need to see your doctor just to confirm whether your man boobs have occurred by your being over weight or you may have Gynecomastia which is a benign enlargement of the male breast. Don't start to panic until you are sure of the diagnosis.
Once you have confirmed which condition you have, then you can sit down and discuss things in a calm and rational manner with your doctor as to what to do next. Information can be easily sourced and as long as you talk about it then you should not have any problems. Being told of which condition you have does not make it the end of the world, all it does is confirm things and then your doctor can advise you further. If you have found out from your doctor that your man boobs have occurred by weight gain then, it's going to be hitting the gym and cutting back on various foods for you unfortunately.
Your doctor should be able to help you with diet and foods that you can eat that will help you lose the weight. If it is Gynecomastia then your doctor can recommend to you various methods to reduce your man boobs, it is not the end of the world if you do have gynecomastia. What happens is that you may need to look at surgery, also the cost involved and the length of time it takes to recover but only do this as a last resort.