My mom gave me the explanation once, my grandfather had somewhat a barrelled chest, and of course, he didn't have CF.
I guess I was fortunate to be "endowed" with a little bit of muscle build, to set off the barrelled chest, though I didn't have enough in the shoulders and arms to really balance myself. However, until I learned to walk with a straight back, the barrelled chest was more noticable.
My new wife, and sometimes guys in my club for Iaido tend to notice a larger chest when I'm changing, but only recently had I been hassled about my mid-section!
I can force my belly out, and look like I'm about 8 months due! (sorta like what EB24 was indicating!) But that sometimes happens unintentional when I'm bloated, too!