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Dietary Fats: Types, Roles, Sources, and More

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Although there’s a lot of debate about carbs these days, just a handful of years ago dietary fat was the most controversial micronutrient.

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In fact, there’s still a lot of confusion surrounding dietary fat, its significance to health, and which types are the healthiest.

With this brief guide to dietary fat, we hope to cut through the noise and address many of the persistent myths about fat so you can understand the importance of this vital macronutrient and how to choose the best options.

What is Dietary Fat?

Fat is one of the three macronutrients, which are nutrients that are required by the body in large amounts. These macronutrients — including fat, carbohydrates, and protein — all provide calories that the body can use for energy.

Fat provides 9 calories per gram, while protein and carbohydrates each provide 4 calories per gram.

In addition to being used for energy, fat plays an important structural role in the creation of cell membranes and hormones. It may also help regulate inflammation (*).

Dietary fat is found in many foods, but mostly in oils, butter, solid animal fats, avocado, dairy products, nuts and seeds, and fatty meats.

Are All Fats Bad?

Starting in about the 1950s, fat began to be considered unhealthy — especially saturated fat and cholesterol, which are found mostly in animals. According to extremely flawed research conducted during the 1950s through the 2000s, saturated fat and cholesterol were leading contributors to heart disease. Additionally, fat was blamed in part for the obesity epidemic since it contains more calories per gram than protein and carbs (*).

During this time, people were heavily encouraged to limit their intake of saturated fat and cholesterol as much as possible, and to swap out these fats for industrially manufactured products like vegetable oil, margarine, and vegetable oil-based cooking sprays.

Unfortunately, we have since learned that saturated fat and cholesterol have very little impact on heart disease, and that highly processed vegetable oils easily become unstable when exposed to heat. Additionally, vegetable oils are rich in pro-inflammatory omega-6 fats and have led to a drastic increase in consumption of these fats in recent decades (*)(*).

In more recent years, we’ve learned that more natural fats — those found in animals and naturally oily plant foods like avocado, olives, and coconut — are the healthiest, while highly processed fats like vegetable oils may be linked to worse health outcomes.

The Role of Fats in Our Bodies

Dietary fat is used to synthesize various hormones, including testosterone and estrogen. Fats are also used to create specialized structures that transport nutrients throughout the body and to form the phospholipid component of cell membranes (*)(*).

Fat, and cholesterol are also used to form the myelin sheath — a protective layer of fat around neurons (brain cells) that helps them to function optimally (*).

Additionally, certain fats — such as omega-3 and omega-6 fats — play a role in regulating the body’s inflammatory response (*).

Types of Dietary Fats

Dietary fat can be divided into three different categories: saturated, polyunsaturated, and monounsaturated.

  • Saturated fat: Saturated fats are fats that are fully saturated with hydrogen bonds, making them extremely stable. They are solid at room temperature and are mostly found in animal fats and coconut (*).
  • Polyunsaturated fat: Polyunsaturated fats are fats that have two or more carbon-carbon double bonds, meaning that the structure isn’t fully saturated with hydrogen. These fats are found in leaner animal foods such as chicken and fish, and also in plant sources.
  • Monounsaturated fat: Monounsaturated fats are foods that contain a single carbon-carbon bond. They aren’t as stable as saturated fats but are more stable than polyunsaturated fats. Foods like olive oil, avocados, and nuts and seeds are rich in monounsaturated fats.

Fat-containing foods usually contain a mixture of one or more types of fat, although one type is usually in a higher quantity than the others.

Additionally, there are specific types of polyunsaturated fats known as omega-3 and omega-6 fatty acids.

  • Omega-3: Omega-3 fats are associated with brain development and heart health. They also play an important role in reducing inflammation. Omega-3 fats are found in fatty fish like salmon and flax seeds (*)(*).
  • Omega-6: Omega-6 fats must be in balance with omega-3 fats for optimal health. A high intake of omega-6 fats paired with a low intake of omega-3 fats actually may increase inflammation. Unfortunately, the introduction of vegetable oils has significantly increased omega-6 intake, while omega-3 intake remains fairly low across the population (*)(*).

Finally, there is the matter of trans fats. These occur naturally in very tiny amounts in some foods, but they can be artificially made by saturating polyunsaturated oils with hydrogen. These manufactured trans fats have been linked to heart disease, and have since been banned in many countries, including the United States (*).

Dietary Fat Sources

Below is a list of various types of fat and which foods are the best sources of each.

Foods High in Saturated Fats

These foods contain mostly saturated fat:

  • Beef
  • Pork
  • High-fat processed meats (bacon, sausage, hot dogs, etc.)
  • Egg yolks
  • Coconut oil
  • Palm oil
  • Eggs
  • Butter and ghee
  • Full-fat dairy products
  • Baked goods made with butter or animal fat

Foods High in Unsaturated Fats

The following foods mostly contain unsaturated fats:

  • Vegetable oils (soybean, corn, canola, peanut, etc.)
  • Vegetable oil-based spreads, margarine, and shortening
  • Olive oil
  • Avocados and avocado oil
  • Nuts and seeds
  • Fish, including salmon and tuna
  • Chicken

Foods High in Trans Fats

In the United States and many other countries, trans fats are banned. For this reason, it’s extremely difficult to find foods that contain trans fats on the label.

You may, however, have some items in your pantry that were manufactured before the ban — like certain vegetable shortenings or packaged snacks. Check to see if they contain an ingredient called “partially hydrogenated oil.” This means that they contain trans fats.

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Choosing Healthy Dietary Fats

With all the conflicting information about dietary fat, it’s hard to know which ones to choose for optimal health. This reference guide can help you choose the healthy fats and oils.

Best Fats for Cooking and Baking

The most stable fats for cooking and baking are solid animal fats, like tallow, lard, ghee, and bacon grease.

Butter is also a great option for baking because of the flavor it adds and the properties that allow it to melt and then resolidify, resulting in a fluffy and flaky end product.

The best plant-based oils for cooking are avocado oil and coconut oil, particularly if they are cold-pressed and unrefined. These oils are derived from naturally fatty foods, so they require less processing in order to extract. They both appear to be more stable than other plant-based oils when exposed to heat, as well.

Best Fats for Dressings, Marinades, and Drizzling

Oils like olive oil, sesame oil, and flax oil have bold flavors as well as lower smoke points, making them ideal for salad dressings, marinades, and drizzling over finished dishes.

Fats to Avoid

Vegetable oils (including soybean oil, corn oil, canola oil, peanut oil, sunflower oil, and safflower oil) should be avoided as much as possible because they are highly processed, unstable when heated, and extremely high in pro-inflammatory omega-6 fatty acids.

Common Misconceptions About Dietary Fat

There are several myths about dietary fat that still persist even today, although we have strong evidence to “bust” them. Here are a few of these myths, along with what current research has to say on the subject.

Myth: Saturated Fat Causes Heart Disease

One persistent myth is that saturated fat causes heart disease because it clogs the arteries, like pouring grease down a kitchen sink.

However, the process of atherosclerosis (plaque formation in the arteries) is a much more complicated process than this, and it’s mediated heavily by inflammation (*).

Research shows that saturated fat and dietary cholesterol don’t worsen this process and therefore are extremely unlikely to be involved in heart disease (*)(*)(*).

Myth: Vegetable Oil is Heart Healthy

A second myth that goes hand-in-hand with the saturated fat myth is that vegetable oils are heart-healthy.

Many people have replaced natural fats like butter and lard with margarine and vegetable oils, for the sake of heart health.

However, research shows that these vegetable oils are heavily prone to oxidation when heated, which can lead to the formation of free radicals that damage the cells and increase inflammation. Additionally, vegetable oils have drastically increased the average person’s omega-6 fat consumption — leading to an imbalanced ratio of omega-6 and omega-3. This also leads to inflammation (*)(*)(*).

Because heart disease is heavily influenced by inflammation, vegetable oils actually appear to be harmful for heart health.

Myth: Fat is Bad Because It’s High in Calories

A final myth is that fat is bad because it’s higher in calories than protein and carbs. It contains 9 calories per gram, while protein and carbs contain just 4 calories per gram.

While it’s true that this could lead to weight gain if you’re eating a lot of fat, trying to drastically decrease your fat intake to reduce calories could also have negative consequences.

Protein is extremely filling, so it’s difficult to eat more than a certain amount at each meal. However, carbohydrates — especially those low in fiber — aren’t as satisfying. If you’re replacing fat with carbohydrates, you may find that you get hungrier more often. A higher simple carb intake could also lead to changes in blood glucose levels, hunger hormones, and food cravings.

The Bottom Line

Figuring out which fats are the healthiest can seem like a daunting task. However, as we’ve learned is the case for other foods, the most natural and minimally-processed options tend to be the healthiest.

Although saturated fat was once considered a villain, these fats are the least processed and the most stable — making them healthier than many other choices.

On the other hand, processed vegetable oils like soybean oil, corn oil, and canola oil may promote inflammation and cellular damage.

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Fat is important for health, but it’s also important to take steps to swap out highly processed vegetable oils for healthier options like animal fats, avocado oil, coconut oil,l or olive oil.

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DiNicolantonio JJ, O’Keefe JH. Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis. Open Heart. 2018 Sep 26;5(2):e000898. doi: 10.1136/openhrt-2018-000898. PMID: 30364556; PMCID: PMC6196963.

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DiNicolantonio JJ, O’Keefe JH. The Importance of Marine Omega-3s for Brain Development and the Prevention and Treatment of Behavior, Mood, and Other Brain Disorders. Nutrients. 2020 Aug 4;12(8):2333. doi: 10.3390/nu12082333. PMID: 32759851; PMCID: PMC7468918.

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DiNicolantonio JJ, O’Keefe JH. Omega-6 vegetable oils as a driver of coronary heart disease: the oxidized linoleic acid hypothesis. Open Heart. 2018 Sep 26;5(2):e000898. doi: 10.1136/openhrt-2018-000898. PMID: 30364556; PMCID: PMC6196963.

Simopoulos AP. An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients. 2016 Mar 2;8(3):128. doi: 10.3390/nu8030128. PMID: 26950145; PMCID: PMC4808858.

Lawrence GD. Perspective: The Saturated Fat-Unsaturated Oil Dilemma: Relations of Dietary Fatty Acids and Serum Cholesterol, Atherosclerosis, Inflammation, Cancer, and All-Cause Mortality. Adv Nutr. 2021 Jun 1;12(3):647-656. doi: 10.1093/advances/nmab013. Erratum in: Adv Nutr. 2021 Oct 1;12(5):2040. PMID: 33693484; PMCID: PMC8166560.

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16 thoughts on “Dietary Fats: Types, Roles, Sources, and More

  1. Love the infographics! Also, that you listed the carbs for each as well. It would have been helpful to have the grams of sugar listed too. This will definitely help when I am trying to decide what meal options are available. Thanks!

  2. I ABSOLUTELY LOVE THIS WEBSITE. I FOUND IT ABOUT 2 WEEKS AGO AND I CAN’T STOP READING THESE ARTICLES. LOVE IT. THANK YOU FOR EVERYTHING THAT YOU DO!!!

  3. Helpful, except two avocados weighing 210 grams are likely very small avocados and combined likely have net carbs between 6-9.
    A typical single weighs about 200 grams.

  4. This is golden, I was literally sitting at my desk freaking out because I have about 300 calories left in the day, 40 grams of fat and 20 grams of protein to get through and I had no clue how to achieve that. I did a lot of googling and then found this. Actually seems like all my concerns lead me back to this website. Pure gold.

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