As my fitness routine has evolved, I've started doing workouts that isolate certain muscle groups. The resistance bands have been awesome, and they were the missing key for me. But I've been doing heavy aerobics for the last couple months just to get improved cardio, and that's been giving me muscle mass in places like my chest.
Even in my younger days when I was in great physical shape, I didn't do much upper body weight lifting, so I've never had man boobs before. Earlier looking in the mirror, I guessed that I'm sporting about a B cup size.
It looks good on me, but it's still a bit disconcerting to catch a glimpse of myself in the mirror. These days looking in the mirror is like looking at someone else!