Q: how do i get rid of the fat under my chest as i want it to be flat. i am a teenager

A: There's no way to lose just the chest fat, but the good news is that you can lose fat over all of your body and thereby lose the chest fat as well. Please read this -- it will introduce you to the program as well as refer you to two other articles that will give you the exact program to follow, one for nutrition, one for exercising. As you read it, please keep in mind that that the nutrition article is targeted more towards adults in suggesting a diet plan. Unless you're very overweight, as a teenager you should not go on a prolonged aggressive diet because it may interfere with your growth. So eat slightly more than the calorie calculator referenced in the article suggests. Aside from that point, the article will tell you exactly what you need to do to lose that extra fat. It's not an easy fix, but if you put your mind to it, you will reap great benefits! Post questions here if you need my to clarify something about the program presented in the article. Best of luck to you!