One of the unique things about fiber is that you’re not digesting all of the calories that you’re consuming.
What do I mean?
There are two types of fiber:
1.Soluble Fiber
2.Insoluble Fiber
Soluble fiber dissolves in water, forms a gel-like substance in the colon, and slows down digestion and nutrient absorption from the stomach and the intestine.
Insoluble fiber does not dissolve in water and is actually left intact and undigested.
Insoluble fiber helps to speed up the passage of food through your stomach and intestine, and it adds bulk to the stool and can help relieve constipation.
The calories that you get purely from insoluble fiber don’t get digested.
For example, if a food has 100 calories and 15 of those calories are from insoluble fiber, then 15 of those calories don't actually get digested from your system.
Only 85 of those calories get digested while the other 15 get excreted.