wherever your body stores fat is where it stores fat; some people have problem areas that aren't problematic for others. if you have a "fat chest" then the only thing that will help with that is getting leaner. so make sure your diet and training are in check. if your nipples are puffy or if you have some minor form of gyno from when you hit puberty then this should be able to help lessen the problem. but for leaning out, ai's can help (controlled estrogen, pulls water out from under the skin, raises natural test levels, etc.) but are far from the most important points; diet first and foremost is what gets you lean (then cardio/training, then supplementation)
As long as he doesn't stay on it for a ridiculous amount of time or dose it too high it shouldn't be an issue. I used test boosters and estrogen controlling products at age 19 since I had somewhat low test levels for my age and estrogen was normal, but wanted to raise test a bit more. I know people say they're useless for people ages 16 to about 21 or so, but in some cases they can be beneficial, just need to be utilized properly
