March 28, 2021

Macronutrients Series: Let’s Break Down Fats

Warning: this post is science-heavy. If you’re into it, please enjoy! If you’re not into it, scroll down to the Bottom Line message.


If you missed it, we covered one of the macronutrients, carbs, a while back. As a reminder, macronutrients (carbs, fat, protein) are what give us energy (i.e., calories) from foods. Think of them as the building blocks of our food. We need all 3, and all 3 have different functions in our body. A well-balanced meal has all 3 macronutrients. This is what helps us 1) get the various nutrients we need, 2) feel satisfied and full after eating.


Buckle your seatbelts! Today we are diving into fat, diet culture’s villain for most of the 1980’s, and ’90’s. Honestly, we’re still coming back from that, although carbs have really taken the heat in the past 2 decades. Fats that we eat are made up of fatty acids. These are basically chains of (science alert!) carbon and hydrogen atoms. Some are short, some are medium, some are long. 


Types of Fats

You may have heard of terms like saturated fat, unsaturated fat, trans fat. The key difference between these types of fats is the shape of these chains.

Saturated fatty acids are straight, and this means they can stack right on top of each other and hence are solid at room temperature.

On the other hand, unsaturated fatty acids have kinks in their shape due to the types of bonds. This makes it hard for them to stack neatly and contributes to their property of being liquid at room temperature.

Trans fats are mostly a product of industrial processing that manipulates the shape of the fatty acid to make it more shelf-stable, and has been associated with increased risk of heart disease. The research is pretty convincing on that point, so the FDA has recently (2015) prohibited food manufacturers from using significant amounts of trans fats.


Food Sources

In general, saturated fats are found in animal products — think meat, full-fat milk and milk products — and also tropical oils like palm and coconut.

Unsaturated fats are found more so in plant products and fish – think nuts, seeds, avocados, oils made from plants, fish and seafood. To go a step further, unsaturated fats can be divided into monounsaturated and polyunsaturated fats (based on the # of double bonds in that chain). You may have heard of omega-3’s and omega-6’s. Both are types of polyunsaturated fats, and a few of them are essential – meaning our bodies cannot make them and we need them from food. Many people, particularly in Westernized cultures, are getting too much saturated fat and not enough unsaturated fats. 

To be clear, foods with fat contain a mixture of different types of fats. Often one of the types is most prevalent in that food, so we associate certain foods with certain types of fat (e.g., butter with saturated fat).

One of our macronutrients, fats, can be found in butter


Why do we need fat?

1) It provides us with energy.

2) Without fat, we would not be able to efficiently absorb quite a few vitamins that NEED fat to get into our body.

3) Our body uses it to make some really important things like components of our cell membranes, structural components around nerves in our brains, and hormones.  


Quick Run-Down on Digestion of Fats

Fats travel through the stomach where they start to get broken down a bit into smaller components. The presence of fat in the stomach slows down the movement of food from the stomach to our intestines, which contributes to us feeling full. Once in the small intestine, bile acids from our liver and enzymes from our pancreas break the fats down to their smallest components. Ultimately the components are packaged into these neat little balls that can move into our lymphatic circulation, then to our blood, and ultimately to fat and muscle tissue to be used or stored for energy. 


Is all this to say you cannot have meat or full-fat yogurt? Hell to the no. But it does mean most of us need to work in more plant foods to get more of the unsaturated fats and less of the saturated fats into our bodies.


Bottom Line: We need fat. Not all fats are equal. Most of us need more fats from nuts, seeds, fish, and less from (land) animal products for maximum nutrition benefits + satisfaction.


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About the Author: Kelly LaVoie, MS, RD, LDN

I'm a Registered Dietitian (RD) based in Chicago, IL. I have worked in both inpatient and outpatient settings, including dialysis, ICU, as well as one-on-one nutrition counseling and groups.


  1. Mike March 29, 2021 at 2:40 pm - Reply

    Everything you needed to know about fats but were afraid to ask. Liked the focus on types, sources, journey through our bodies, and message: more unsaturated, less saturated.

  2. cpruz2790 April 3, 2021 at 2:56 pm - Reply

    Thanks, Mike! Glad you found the post helpful :)

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