He did it while I was washing...

I told him to complete his business, he insisted he did. While I was washing his backside, he did it.

Why do some people pass motion everyday while others don't? And why do they do it almost at the same time everyday?

Bowel habit is dependent largely on diet. If one eats a lot of fiber than one will pass motion more often. It is also related to water intake. If one takes insufficient fluids, one is more prone to constipation. The normal frequency of bowel movement varies a great deal from individual to individual. It can be as often as several times a day to once in 2 weeks. This is why a change of frequency is more important to a doctor than the actual frequency.


Source: Singapore Science Centre