By Roberta H. Anding, MS, Baylor College of Medicine and Texas Children’s Hospital

Edited by Kate Findley and proofread by Angela Shoemaker, The Great Courses Daily

Roberta Anding explores the many fascinating functions of fat. She also delves into good fat versus bad fat.

Functions of Fat

What are the functions of fat? Fat is an energy source with nine calories per gram. That’s more than double the calories from an equal amount of protein or carbohydrate.

Through thermal insulation, subcutaneous fat right below the surface of the skin protects vital organs including the heart, liver, kidney, spleen, brain, and spinal cord from trauma. It can also serve as a hunger suppressant, helping you feel full longer.

Additionally, fat is a transport medium, meaning that it transports fat-soluble vitamins from the gut into the blood, where they’re going to be carried by other transport proteins. Thus, you need to have some dietary fat for the utilization of vitamins A, D, E, and K.

Fat can slow digestion, which gives the body time to absorb nutrients from other food. Fat is necessary for the production of many regulatory hormones and structural components such as brain development and function. In fact, your brain has such a significant amount of fat that if somebody calls you a “fathead,” it’s actually a compliment. 

Good Fat Versus Bad Fat

What about good fat versus bad fat? As our calorie intake has risen over the past few decades, many extra calories come from these hidden fats and sugars. 

Total fat has actually declined in the American diet, but the average American is still consuming about 15% of total calories as saturated fat. Most public health organizations recommend that we keep our saturated fat intake to 10% or less of total calories. 

In fact, some estimates suggest that it should be in the range of 7% to 10% of total calories. This is because saturated fat can cause cholesterol levels to rise in our blood, leading to heart disease.

In the typical American diet, we get about 34% of our saturated fat from plant sources, including coconut oil and palm oil. Animal sources contribute to approximately the remaining two-thirds. Health professionals recommend replacing at least some of the saturated fat and all trans fats with non-hydrogenated mono- (one double bond), and poly- (many double bonds) unsaturated fats such as olive oil and safflower oil.

How can we do this in a practical way? First, we can reduce high-fat animal foods, such as ribs and cheese, with lower fat foods such as chicken and fish. For example, an eight-ounce rib eye has about 65 grams of fat, whereas an eight-ounce chicken breast has about 25 grams of fat. 

Omega 3s and 6s

Essential fatty acids fall into two different camps: omega-3 and omega-6 fatty acids. These fats must be consumed in the diet. 

Omega-3 fatty acids are highly unsaturated fat. The term “omega-3” refers to the position of the first double bond in the long fatty acid chain, and the double bond occurs three carbons in. 

Most research studies suggest we don’t consume adequate amounts of this fat in our diet. This fat is needed for the production of hormone-like compounds known as prostaglandins. 

The specific prostaglandins formed from these omega-3 fatty acids are anti-inflammatory. Just as you take aspirin to reduce inflammation, omega-3 fats have an anti-inflammatory function. They confer mostly positive health benefits, and the risks are only associated with excessive intake.

Omega-3s are found in the oils of coldwater fish such as herring, mackerel, sardines, and shellfish. Why coldwater? 

The more double bonds the molecule contains, the more liquid the fat is. The fish swimming in really cold water are not going to have a freezing of that cell membrane, and thus that cell membrane is not going to solidify because that fatty acid is so polyunsaturated. It remains fluid in a very cold environment. 

Flaxseed oil also contains essential omega-3 fatty acids, including linolenic acid, but it’s less powerful than that found in fish. To get an adequate amount of omega-3 fatty acids in your diet, the American Heart Association recommends two servings of fish a week.

If you don’t like fish, you can use fish oil supplements. Benefits of omega-3s include improvement in our blood lipid profile, plasma triglycerides, and blood triglycerides, and as triglycerides go down, it actually raises the beneficial high-density lipoprotein (HDL) cholesterol.

Research suggests that omega-3s reduce heart disease risk and mortality rates associated with ventricular fibrillation and sudden death. Studies also support their use in the prevention of Alzheimer’s disease and any inflammatory disease. 

Omega-6 fatty acids tend to be over-consumed in the American diet. They’re found in meat, corn oil, safflower oil, and sunflower oil. 

They act in opposition to the omega-3 fatty acids by increasing inflammation. The challenge in the American food supply is when we have beef that is corn raised. 

They are getting a higher percentage of omega-6 fatty acids in their feed, which translates into higher omega-6 fatty acid content in the meat. Thus, the best thing you can do is look for grass-fed beef or limit your beef consumption while increasing your consumption of omega-3s.

This article was edited by Kate Findley, Writer for The Great Courses Daily, and proofread by Angela Shoemaker, Proofreader and Copy Editor for The Great Courses Daily.