Balance is surprisingly heavily dependent on sight. If you close you're eyes you'll notice how it becomes much harder to hold your balance.
Some people claim that people who can't balance on one leg, with their eyes closed, for more than 2 seconds are more likely to die before the age 65 than people who could balance for more than 10 seconds.
That statement might sound really dumb, but that's until you consider it from another perspective. It would be much easier for a healthy person to balance on one leg in comparison to a morbidly obese one. Just based on statistics, one of them is more likely to live a longer life.
That's mainly based on my assumptions since the only comparison that I have available would be myself. Although a bit wobbly, it was definitely easily doable.