Fiber is a type of carbohydrate in your diet that passes through your system without getting digested. Your body does not use fiber to break down fat. Instead, fat breakdown requires the actions of substances called enzymes, which interact with the fat content of your diet and release usable materials called fatty acids.
Basics
To take advantage of the energy and nutrients in the foods you eat, your body must first find some way to digest these foods and break them down into their constituent parts. This breakdown process, called catabolism, is the first stage of your body's mechanism for energy conversion and use, known as your metabolism. After catabolism, your body takes the individual components of your food and uses them to make new materials that support your internal functions and everyday survival. This reassembly process, called anabolism, is the second stage in your metabolism. Your metabolism is active in one form or another 24 hours a day throughout your entire life span.
Fiber's Role
When you consume dietary fiber, it is not digested in your body and doesn't play a direct role in your metabolism. Instead, fiber passes through your digestive tract more or less intact and gets eliminated in your feces. On its way through your tract, one form of fiber --- called soluble fiber --- helps slow down your digestive process. Another form of fiber, called insoluble fiber, speeds up digestion and increases the overall bulk or size of the stools you produce.
Fat Breakdown
When you eat foods that contain fat, digestive actions in your stomach create substances called triacylglycerols, according to "Interactive Concepts in Biochemistry." These triacylglycerols then proceed to your small intestine, where they get suspended in a liquefied state by secretions from your gallbladder. Further down your small intestine, an enzyme called pancreatic lipase breaks apart triacylglycerol molecules and creates substances called fatty acids, as well as another substance called glycerol. Fatty acids and glycerol then get attached to other molecules in your small intestine and pass from your intestine to your bloodstream.
Considerations
Depending on your immediate needs, the fatty acids in your bloodstream get used right away for energy or get stored as energy reserves in your fat cells. Although fiber doesn't help you break down fat, it does play several important roles in your everyday health, including helping you maintain the health and structural soundness of your bowels, promoting regular bowel movements, lowering your blood levels of harmful cholesterol, controlling your levels of blood glucose and helping you limit your food intake by making you feel full when you eat. Consult your doctor for additional information on fiber's effects, as well as the way in which your body processes and uses fat.
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