Fat digestion begins before food even enters the stomach, with chemical digestion starting in the mouth. The body continues digesting fat as food moves through the digestive tract.

Fats are a type of lipid that is vital for health. They provide energy, cushion the organs, help cells grow and reproduce, and keep the body warm.

Keep reading to learn more about fat digestion, including how it works, which fats are hardest to digest, and more.

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Lipids are not water soluble, which means that water cannot absorb them or break them down. Most of the body’s digestive enzymes are water-based, so the body has to use special enzymes to break down fat throughout the digestive tract.

The body begins breaking down fat in the mouth, using enzymes in saliva. Chewing increases the surface area of foods, allowing the enzymes to break down food more effectively. The most important chemicals that help with fat digestion in the mouth are lingual lipase and phospholipids, which turn fats into small drops.

While some fat digestion happens in the stomach, most of this process occurs in the intestines.

The next step in fat digestion happens when gastric lipase in the stomach further breaks down fats. As the stomach contracts, this process intensifies. The stomach can convert close to 30% of fats into diglycerides and fatty acids by about 2–4 hours after eating.

Next, the contents of the stomach, including the diglycerides and fatty acids, travel to the small intestine. The liver releases bile, which contains lecithin, bile salts, and emulsifiers that help further break down fats.

Bile grabs onto the fats, and the emulsifiers increase their surface area, making them easier for digestive enzymes to act on.

Following this, enzymes break apart fatty acids. Lipase from the pancreas further digests fats into monoglycerides and fatty acids. Bile again grabs onto the fat to help move it to the tiny hair-like projections of the intestines. These projections, called microvilli, help transport the fats into the cells of the digestive system.

From there, the body must absorb fats. To do this, the broken down components of the fats regroup into triacylglycerols. These can join together with cholesterol, phospholipids, and a protein to form lipoproteins. Lipoproteins enter the lymphatic system, and the body then releases them into the bloodstream.

As fat digestion requires numerous enzymes, various conditions can affect this process and, as a result, absorption. Liver disorders, small bowel syndrome, and problems with the small intestine can make it more difficult for the body to digest and absorb fat. Due to this, some people with these conditions may notice fatty stools.

A 2018 study suggests that solid fats — those that are solid at room temperature, such as butter — are harder for the body to digest than fat droplets.

The study used a model of the human digestive system to see how quickly enzymes could break down the two types of fat. The digestive model broke down solid fats about half as quickly. This finding suggests, but does not prove, that solid fats may present more digestive issues. It is important to note, however, that the study did not look directly at humans and used only one type of fat emulsion.

The type of fat is not the only factor determining how hard a food is to digest. Certain foods, such as fried foods, are more difficult for the body to digest and more likely to cause digestive problems.

Digestive issues can also result from food sensitivities in some cases, so people with a history of digestive problems may wish to try keeping a food diary to track their diet and symptoms.

Effective fat digestion is critical for overall health, as the body needs fat to carry out many of its functions. Effective fat digestion may even play a role in maintaining a moderate body weight. People may be able to improve their fat digestion by:

  • Eating a lower fat diet: A 2018 study found that a typical high fat Western diet may promote the development of bacteria in the gut that cause a person to absorb more fat, potentially leading to weight gain.
  • Eating healthful fats: People should aim to include healthful fats, such as avocados, nuts, coconut oil, and fish, in the diet. At the same time, they should reduce the intake of processed fats, red meats, and fried foods.
  • Treating health conditions: It is important to get treatment for any chronic or long-term medical conditions, especially those affecting the liver and digestive system. Problems with these organs can make it more difficult for the body to digest nutrients, including fat.
  • Protecting liver health: The liver makes bile salts that play a key role in digesting fat. People can help protect their liver by moderating their alcohol consumption and refraining from using recreational drugs.

Although some natural and alternative medicine proponents argue that taking certain digestive enzymes or supplements may improve fat digestion, there is not enough scientific evidence to support this claim.

Fat digestion is a complex process that takes time and requires a functioning liver, pancreas, stomach, and small intestine, as well as numerous digestive enzymes.

People who worry that they may not be properly digesting or absorbing fat should contact a doctor, as no home treatment can reliably improve fat digestion.