I'm glad you asked. A lot of people have questions about bathroom issues but are afraid to ask.

So first, let's talk about fiber. Fiber is the part of food that you can't break down. There's a lot of it in fruits, vegetables, and wholegrain foods. If you drink a soda, all of the food in it can be broken down. Some becomes water in your body. Extra water leaves as urine or sweat. If the food you eat has protein in it, some of that leaves in the urine too. The rest you actually breathe out as carbon dioxide.Really. Fiber is the plant material that our bodies can't digest, so it ends up in feces ("poop").

Once you swallow food, your conscious mind is not in charge of what happens to it. The rest of the process is controlled by your autonomic nervous system, which all of your basic life supports. One thing it does is move food and feces through your intestines by making the intestines squeeze the food along. When a place in the wall of the gut senses that there's stuff there, it squeezes it along to the next place.It usually takes about 39 hours for food to go through a woman's entire digestive system. In children and teenagers it's probably faster.

The fiber a person eats absorbs water, making the feces bigger and softer. That means that it tells the gut to push it along more often, and makes it easier to push along. So fiber speeds up the trip. Eating fiber can have an effect in hours, or it may take days.

If you didn't eat any fiber at all, you would not need to defecate (go"number 2") very often. You would have some feces, just because the cells in your intestines are constantly being shed, but there wouldn't be much. This might seem like a pretty good thing. Finding a bathroom can be inconvenient. However, fiber is actually very important in our diet. It helps keep cholesterol low, it helps control blood sugar, it keeps us from over-eating, and it keeps our digestive systems healthy.

For more on the whole story of your digestive system, check out:

You can't digest it, so you have to flush it through your body. The more of it you eat, the more of it you need to get rid of.

It keeps water in our digestive systems. The extra water takes up extra volume, just as cooked oatmeal takes up more room than dry oats. So the body needs to empty the digestive system more often.

Fiber makes you go to the bathroom because your body does not digest it into soup the way it does fat, protein, or sugars. Instead, fiber (which is really just tough plant matter...imagine eating tree leafs or bark)makes it easier for your intestine to bundle up the food you eat so that it can move it through your gut. It sort of works like a sponge for the nutrients in your food...which is good for digestion but also leaves a big sponge undigested at the end of your digestive tract. Your intestine moves that sponge faster because it can grip it well, and then your colon fills up faster and you have to go to the bathroom to get rid of all that fiber. Some people liken this to getting your digestive tract"cleaned out" by the sponge, which is generally why fiber is a good thing.