Is it difficult to treat breast protrusion alone?

I am writing this to seek advice because a close male acquaintance is having trouble.

A while ago, I went out to play golf with some friends, and the caddy cautiously told one of them, "Your breasts seem bigger than most women's."

Although it was a joke, the person involved seemed to be aware of it, and it seems like he has been stressed out by this issue on a regular basis.

This person is not obese all over his body, but his chest area is particularly bulging like a woman's breasts.

It's not a droopy shape, but it's noticeable at first glance, so I always pay attention to it when I wear clothes.

Even when looking at it from people around me, it seems like you have deep concerns. In this case, is it possible to solve it with simple exercise or diet?

Or I'm wondering if I should get some kind of medical treatment called 'gynecomastia'.

Is the treatment process complex or difficult?

I would appreciate any advice or experiences that could be of practical help to my friends.