It is actually connected to your bladder and it remains the same length regardless of how much weight you gain. You can convert an “outie” (protuberant) belly-button to an “innie” (deep) belly-button via a plastic-surgery procedure called an “umbilicoplasty”.
I am occasionally reminded of how interesting it is that we do not lose our naval/belly-button over time. All eight-billion of us are walking around with a physical anomaly that has served absolutely no function at all since we were brought into the world. Unless you happen to have a piercing there, we are blind to it most of the time.
Is there absolutely ANY way to change an outie belly button into an innie?
Is your belly button connected to anything on the inside? And if so, will it be “anchored” in the same spot if you gain weight?