Nutrition Basics: Eating Fat Does NOT Make You Fat


While everyone seems to agree that protein is a necessary component of a healthy diet, there is still loads of controversy about fat.  Should we eat it or not?  Are there good kinds and bad kinds?  Does eating fat make us fat?

It’s really important that we understand fat because it is a critical component of our physical bodies… and I’m not just talking about our fat stores.  As such, I want to be sure that you know how to use dietary fat to your advantage, while also dispelling any myths about fat that might be lurking in your mind.

Now, you know that getting through all that information will take a lot of words, so feel free to skip to the headers that interest you, if you don’t have time to read the whole thing!  (I promise my feelings won’t be hurt. 🙂 )

What is fat?

Fats are simply any organic compound that cannot mix with water.  This somewhat generic definition means there are all sorts of things that are considered a “fat” that are quite different from each other, with the only uniting property being the fact that each of them cannot be combined with water.  In fact, all of these words describe some type of fat related to humans:

  • Dietary: triglycerides, cholesterol, essential fatty acids, omega-3 fatty acids, omega-6 fatty acids, short chain fatty acids, medium chain fatty acids, long chain fatty acids, monounsaturated fats, polyunsaturated fats, saturated fats, trans fats, hydrogenated fats, oils, tallow, lard, grease, butter, shortening, MCT oil
  • Physiology: triglycerides, total cholesterol, LDL-C, HDL-C, VLDL, IDL, adipose tissue, brown fat, white fat, visceral fat, subcutaneous fat, lipids, chylomicrons

For completeness, some of these words are used to be more or less specific in describing the same thing (example: omega-3 fatty acids are a type of essential fatty acid) or to describe different parts of the same thing (example: triglycerides are made of a glycerol back bone with 3 fatty acids attached; those fatty acids might be short, medium or long chained).

How does fat get used in the body?

Fat is essential for proper body function.  I’m going to repeat that because it’s important that you understand this… your body needs fat in order for it to function the way it is meant to function.  The following are the main ways that the body uses fat:

  • Cellular structure as a member of the cell’s membrane (this is why you are waterproof… the fat that outlines the cells of your skin prevent you from being a sponge)
  • Cognitive function… because your brain is nearly 60% fat
  • Absorption and storage of fat-soluble vitamins (A, D, E and K).
  • Insulation:
    • Under the skin and in around the muscles which helps with temperature regulation and protection of your organs
    • Of your nerves which ensures messages get from your brain to their intended recipient
  • Energy creation (when needed)… in fact, the cells of your large intestine get energy exclusively from butyrate (a short-chain fatty acid created by the bacteria that live there).
  • Energy storage (you can create and store a lot more fat than you can glycogen)
  • Transmission of messages between cells
  • Precursor for other elements in the body (example: cholesterol is turned into vitamin D, testosterone, estrogen and bile acids)
  • Sequestration of fat-soluble toxins that the body can’t eliminate

What foods contain fat?

Many of the foods in our diet contain fat with some foods, like spinach, containing a little bit of fat (0.1 grams in 1 cup) and some foods, like ghee (clarified butter), being 100% fat.  Most fruits, vegetables and legumes contain small amounts of fat.  The most obvious exceptions to this are avocados, olives and coconuts.  Nuts and seeds are plant foods that are high in fat, while animal products range from moderate amounts of fat (ex: whole eggs) to 100% fat (ex: butter, lard).

What are good fats and what are bad fats?

Now this is where things might get a little bit interesting because our understanding of how dietary fat affects the body has changed immensely in the last 20 years.  Unfortunately, many people are still getting information based on outdated research.

The only fat out there that is always bad is trans fat.  Let’s just start with the basic fact that trans fats were created by scientists in a lab.  And you know that I think any “food” that was created in a lab is not good for us.  But rather than ask you to eliminate all trans fats from your diet based on that alone, research has clearly shown that trans fats increase our risk for cardiovascular and other chronic diseases.  They cause inflammation throughout the body, decrease our HDL levels, increase our LDL levels, increase fat storage, and cause our cells to resist the effects of insulin (which you probably know is one of the factors in diabetes).

The other fats that have been called “bad” in the past are the saturated fats (so called because their carbon atoms are “saturated” with hydrogen atoms).  These are the fats that are solid at room temperature like the fat in meat, chicken, butter and cheese.  We used to think that all saturated fats were bad for us, raised blood cholesterol and caused heart disease.  What we are learning is it’s just not that simple.  Our bodies use saturated fats to provide structure in many of our cells and the source of the saturated fat seems to be more important than the fat itself.

The other thing we know now is that not all unsaturated fats are great for us.  Unsaturated fats are liquid at room temperature, like oils, and so it seems that their fluid state would be better in our bodies than those that turn solid.  But we didn’t take into account the large amount of processing that goes into creating many of the industrialized oils like corn and soybean oil that are used for deep frying food.  Nor did we consider that even unsaturated fats can go rancid (ie, spoil) and rancid fats are not good for us (one example is that they can initiate cancer growth).

So, the goal is to eat “good” fats as much as possible, which include:

  • Grass-fed land animals (this includes meat and dairy products)
  • Free range poultry (this includes the animal and eggs)
  • Unspoiled plant fats (like good oils, seeds and nuts)

And do your best to avoid “bad” fats:

  • Trans fats (which often show up in processed and deep fried foods)… really we should just eliminate this one all together!
  • Grain-fed land animals (this includes meat and dairy products)
  • Caged poultry (this includes the animal and eggs)
  • Spoiled or highly processed plant fats (rancid oils, seeds and nuts or overly processed oils — check out this Cooking Oil Comparison Chart as a guide)

What happens if we eat more fat than we need?

I’m sure it’s obvious, but if we eat more fat than we need, then we store the rest as… fat.  (Clearly, that’s not nearly as earth shattering as knowing that excess protein and excess carbohydrates get stored as fat!  Ha!)

The key thing here is that the body does not necessarily store dietary fat as body fat.  It only does this when the fat consumed exceeds what is needed for the other functions mentioned above.

As well, the body does lots of different things with fat, so eating fat does not automatically mean that your blood work (LDL-C, HDL-C, total cholesterol and triglycerides) will be out of whack.  (It is beyond the scope of this article, but if you are interested in science-based, accurate information about blood lipids, check out this excellent article.)

When does the body break down fat stores?

Fatty acids are a rich source of energy as they provide 9 calories for every gram, which is more than double the 4 calories available in a gram of carbohydrate.  The body will pull fat out of the adipose tissue (ie, fat cells) when there is not enough energy being provided by the diet or from the breakdown of glycogen.

What’s the story with “ketogenic” diets?

When fat is released from the fat cells to be used as energy, it becomes energy in one of two ways:

  • It enters the cell and then enters the mitochondria where it is turned into energy, or
  • It is taken up by the liver which turns it into ketone bodies.  The liver then releases the ketone bodies into the blood stream where other cells will pick up the ketone bodies and burn them for energy.

Note that most cells in the body can pick up the fatty acids directly from the blood and turn them into energy.  However, the brain cells and red blood cells must receive ketone bodies for energy, if there is not enough energy supplied by carbohydrates.

Ketogenic diets are low in carbohydrates and high in fat with the specific purpose of pulling fat out of our fat stores, which ultimately forces the liver to create ketones in order to provide energy to the brain and other cells.  From a medical perspective, ketogenic diets have primarily been used to prevent epileptic seizures.  However, there is increasing interest in the use of ketogenic diets to prevent other cognitive diseases like Alzheimer’s disease, to reverse metabolic syndrome, and to treat diabetes.

As well, diets and cleansing protocols that restrict carbohydrate intake result in the person entering a state of ketosis (ie, the body is using ketones for energy).  The purpose is to get the body to break down fat stores (called lipolysis), and this only happens when there is not enough glucose for energy.  To state that more clearly, you cannot break down fat stores in the body without eventually creating ketone bodies to keep your brain fed.


Whew!  If you got this far, thank you for reading all the way through.  I know it is a lot to take in.  Hopefully, you learned something new and have a clearer picture about what dietary fat is, why it is so crucial to our well-being, and how to get the good kind in your diet.

If I didn’t answer a question you have about fat, let me know about it in the comments.  And if you know someone who is avoiding eating fat because they think it’s bad for them, please share this article with them!


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— Hall J. Guyton and Hall Textbook of Medical Physiology. 12th ed. Philadelphia, PA: Saunders Elsevier; 2011.
— Mankad R. Does grass-fed beef have any heart-health benefits that other types of beef don’t? In Diseases and Conditions: Heart Disease.  Accessed March 17, 2015.
— Perjési P, Pintér Z, Gyöngyi Z, Ember I. Effect of rancid corn oil on some onco/suppressor gene expressions in vivo. A short-term study. Anticancer Res. 2002;22(1A):225-30.
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— SELF Nutrition Data. Spinach, raw. In Nutrition Facts. Accessed March 17, 2015.
— The World’s Healthiest Foods. Chicken, pasture-raised. Accessed March 17, 2105.

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