Back to Basics: What is Fat?

Fat –– What is it and Why do we Need it?

Fat is one of three macronutrients, the other two being carbohydrates and protein. All three are needed to maintain optimal health. When it comes to fat, it can sometimes have bad rap because many people don't know what its function in our body is, and why it's so important.

So, What is Fat?

Fat is a type of lipid. The types of lipids we usually see in food are fats and oils. You can usually differentiate the two based on how they look. Fats are usually solid at room temperature, like butter, while oils (also a fat) are typically liquid at room temperature, like extra virgin olive oil. Most of the fat we consume is in the form of triglycerides, which also happens to be the way fat is stored in our bodies. When it comes to the fat we eat, there are a few different types –– saturated and unsaturated fat. Unsaturated fat can be split into two sections, monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs).

Saturated Fats

Saturated fats are typically going to be animal fats (with a few exceptions), and are usually solid at room temperature. Animal fats usually contain 40-60% saturated fat. An example of this would be butter, cream, and whole milk. Coconut oil is an example of a plant based saturated fat.

Unsaturated Fats

Unsaturated fats consist of monounsaturated fats (MUFAs) and polyunsaturated fats (PUFAs). Both of these are liquid at room temperature and come from plant sources. Plant fats usually contain 80-90% MUFAs and PUFAs. Some foods containing MUFAs are extra virgin olive oil , canola oil, flaxseed, walnuts, and cashews. PUFAs can be found in canola oil and safflower oil. Unsaturated fats are considered to be healthy fats.

Do you need fat in your diet?

Fat plays many important roles in the body. Essential fatty acids help regulate key physiological functions like blood clotting, expansion/contraction of blood vessels, inflammation, and GI motility. These essential fatty acids are special because they need to be consumed in our diet. These consist of omega 6 (found in vegetable and nut oils) and omega 3 fatty acids (found in fish, leafy green vegetables, canola oil, walnuts, and flaxseed). Omega 3 fatty acids are a vital component in our cell membranes in our body, provide energy, and have functions in our immune system, blood vessels, lungs, and heart.

How are fats used in your body?

In the body fat is used in many ways.

  • Body fat can be used as an energy source during times of rest, exercise, or low energy intake. Anywhere from 30-70% of our energy used by muscles and organs during times of rest is from fat. This percent can depend on your physical activity level, weight, and your fat consumption.
  • Fats are used in the body to maintain cell function.
  • Fats are an important part of our cell membrane and help to determine what transports in and out of the cell. Fats also allow for the transport of fat soluble vitamins (AEDK) which means they help you absorb fat soluble vitamins.
  • Fats play a role in protection. It helps to protect our organs, as well as helping to insulate and retain our body heat.
  • Fat helps us feel full. Fat provides our body with more calories per gram than either carbohydrates or proteins do. Fat also takes longer to digest and help us to feel more satiated.

What are healthy fats?

Unsaturated fats (MUFAs and PUFAs) are viewed as the healthy fats and it's no surprise because they have numerous beneficial health effects, while saturated fats can be associated with worse health outcomes. Unsaturated fats lower bad cholesterol (LDL) and triglycerides, as well as reducing your rate of cardiovascular disease. Saturated fat, on the other hand, is associated with increased risk of cardiovascular disease as well as higher bad cholesterol (LDL) levels.

Healthy fat food sources

Unsaturated fats can be found in various foods, including nuts, vegetables, and fish. Most vegetable oils are a great source of unsaturated fats and contain a mixture of MUFAs and PUFAs. When choosing a protein, it's important to look for sources with less saturated fat. Lean cuts of meat, beans, lentils, salmon, herring, sardines, and nuts are a few of the protein options that are lower in saturated fat.

How much fat should you eat?

Fat should account for 20-35% of the total calories in your diet. When it comes to omega 3 and omega 6, it's important that you are getting enough in your diet because as mentioned before, these fatty acids are essential and need to be consumed through food. The adequate intake (AI) for omega 3 is 1.1 g/day for adult women and 1.6 g/day for adult men, and the AI for omega 6 is 12 g/day for adult women and 17g/day for adult men.

Written by Isabelle Hammack
Reviewed by Kelly Powers, MA, RDN, a Registered Dietitian Nutritionist who takes a holistic approach to nutrition and health. Kelly is a recipe developer with a food blog highlighting whole foods, simple recipes, and her life in San Francisco. She’s the creator of 52 Weeks, a weekly meal plan program that helps users get back in the kitchen and feed themselves well. Kelly is also a co-founder of Olivaio.


Thompson, J., & Manore, M. (2009). Nutrition an applied approach. San Francisco, Calif.: Pearson, Benjamin Cummings.

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