The amount of fiber in bananas may surprise you, and considering that dietary fiber is one of the most important components of a healthy diet, increasing your banana intake may be a good idea.
Soluble vs. Insoluble Fiber
Before we can delve into the fiber in bananas, it is important to understand the difference between soluble fiber and insoluble fiber. A healthy diet should be composed of foods that contain both insoluble and soluble fibers. 
Soluble fiber is able to absorb water and swell up, forming a soft, gel substance in the body, and slowing the digestive process. This is particularly important for those who are watching their blood sugar.
Insoluble fiber does not absorb water, and can, therefore, speed up the digestive process, helping to stimulate peristaltic motion and regulate bowel movements.
Content of Fiber in Bananas
In a medium-sized banana, there are just over 3 grams of dietary fiber, only 1 gram of which comes from soluble fiber and the rest of it from insoluble fiber. Given that a normal diet should have a balance of insoluble and soluble fiber, bananas are considered a good source of fiber. Representing only 12.5% of our daily requirement for fiber, however, bananas are not recognized as a rich source of this key nutrient. There are many other foods – including other fruits and vegetables – that are better sources of dietary fiber than bananas. Some of the best examples are mangos, persimmons, guavas, artichokes, Brussels sprouts, and broccoli. 
If you want to use bananas to boost your fiber intake, look for bananas that are riper. As a banana ripens, the resistant starch is converted into soluble pectin, which is easy for the body to digest. An unripe banana will provide less usable fiber for your body. 
Why is Fiber Good?
Fiber is a critical part of our diet, as it affects many different areas of health, including cardiovascular strength, diabetes, blood pressure, and digestion, among others.
The soluble fiber in bananas can help to balance cholesterol levels, as fiber can scrape excess cholesterol and remove it from the cardiovascular system before it can be oxidized. 
As mentioned earlier, dietary fiber is needed to stimulate peristaltic motion, which pushes bowel movements through your body. Fiber can also cut down on symptoms of bloating, cramping, constipation and diarrhea, depending on which type of fiber you favor within your diet. 
One of the often-overlooked benefits of dietary fiber in the diet is the impact that it can have on blood sugar levels. Dietary fiber can regulate the release of insulin and glucose, which is important for diabetic patients and those who are at high risk for developing this disorder.