Although dietary fats tend to have a bad reputation, they contain large amounts of energy and can be important energy sources. Fats are often large, complex molecules, and their digestion usually takes longer than that of simpler molecules like carbohydrates. Fats are present in a variety of foods, including dairy products, meats, vegetable oils and nuts.
Emulsification
Fats are hydrophobic molecules, meaning that when they are placed in water, they clump together into large aggregates reducing the amount of surface area exposed to water. The first step your body takes to digest fats is to break up these large clumps. Your body accomplishes this process using compounds called bile salts, which are produced by the liver, explains the National Digestive Diseases Information Clearinghouse. Bile salts dissolve the clumps of fat into tiny droplets, similar to the way detergents dissolve grease on dishes.
Hydrolysis
Once your body dissolves the fats into small droplets, these fats are often in the form of molecules called triglycerides, which is made up of a glycerol molecule and three fatty acids. Fatty acids are a type of molecule known as a carboxylic acid, which has a long chain of carbon atoms. The next step of digestion is to break these triglycerides into simpler molecules. An enzyme called lipase, which your pancreas produces, chews up triglycerides into monoglycerides and fatty acids, Colorado State University explains. A monoglyceride is similar to a triglyceride, except that only one fatty acid is attached to the glycerol molecule instead of three.
Absorption
After your body breaks triglycerides into monoglycerides and fatty acids, they remain dissolved in bile salts and form small droplets known as micelles. As the micelles travel through the digestive tract, they come into contact with the cells that line the digestive tract, and these cells absorb them through their cell membranes.
Transport
Once intestinal cells have absorbed monoglycerides and fatty acids, they reassemble them into triglycerides, the form of fat most commonly found inside your body. For transport, your body packages triglycerides together with protein and cholesterol into particles called chylomicrons. The intestinal cells then secrete chylomicrons into the lymph vessels, which eventually flow into the bloodstream. Once fats are in your bloodstream, your body can transport them to wherever it needs them, breaking them down for energy or storing them as fat.
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