Is it a good thing to show some kind of self-irony or can it possibly backfire?

Take this set for instance: I met a friend during lunch break and he was with some of his male and female coworkers. I told them I was working out yesterday, to which one of the girls replied (jokingly), that she could indeed see my belly getting flatter (I am by far no thick person), to which I replied something among this lines:

"I know right? I actually looked in the mirror today and thought, wow, my belly is getting really flat these days". She, as well as the other people nearby were laughing at it and she was smiling at me, but in retrospect don't know if self-irony is conductive or just the opposite.