Male Gynecomastia

I'm curious about how to distinguish between weight gain and gynecomastia.

People with a lot of flesh also have flesh in the chest area. So, I never thought it was gynecomastia.

While participating in this event, I suddenly wondered whether the protruding chest was simply fat or gynecomastia.

I'm curious about how the two are different.

They look similar on the outside, but is there a way to tell them apart?