The Complete Guide to Dietary Fats (the simple version!)

Not sure which fats are healthy and which ones aren’t? This article explains everything you need to know about dietary fats so you can make the best food choices for your health. Keep reading to learn which fats you need to live, which fats you should avoid, and what you should do if you’re trying to lose weight.

This post may contain affiliate links. See my full disclosure here.

Dietary fats.

Talk about a confusing topic!

There are saturated fats, monounsaturated fats, polyunsaturated fats, solid fats, liquid fats, artery-clogging fats, skin-nourishing fats. And the list goes on.

I’ll be the first to admit that I was severely under-educated on the topic of dietary fats until very recently when I decided to sit down and figure this whole thing out. It turns out that dietary fat isn’t as complicated a subject as I thought it would be. Once I understood the basics, I was able to see why certain foods are generally accepted as healthy while others are almost unanimously deemed unhealthy.

It all finally makes sense!

And while I’m so happy that I finally grasp the elusive concept of fats, I’ll tell ya that it took hours and hours of research to get here. I spent the better part of two days scouring medical websites and poring over the massive 2015-2020 Dietary Guidelines for Americans report published by the U.S. Department of Health and Human Services and U.S. Department of Agriculture.

I’ve done the boring enlightening research for you, so let me share with you the simplified version of everything I’ve learned!

In a nutshell, I’ll explain:

• Why you need fat in your diet
• Which types of fat are healthy and which ones aren’t
• How the different types of fats affect your health
• Where to find the best sources of good fats
• Which foods you’ll want to avoid since they’re loaded with bad fats
• Whether oil is a healthy source of good fat
• How to approach fats when you’re trying to lose weight

And so much more!

So go ahead and get comfy so you can learn all about the fascinating world of dietary fats!

Introduction to Dietary Fats

Let’s start with the basics.

What are dietary fats?

Fat is one of the three macronutrients (fats, proteins, and carbohydrates) and is a source of energy.

Dietary fats can be grouped into four main categories depending on their chemical structures and physical properties. There are:

1. Saturated fats
2. Trans fats
3. Monounsaturated fats (MUFAs)
4. Polyunsaturated fats (PUFAs)

Although all four types of fats are sources of energy, they affect our bodies differently. That’s why we say some fats are good and others are bad. I’ll explain why in the next sections, but for now, keep these two things in mind:

• Saturated fats and trans fats are the bad fats; they’re the least healthy of the four types of fats.
• Monounsaturated fats and polyunsaturated fats are the good fats; they’re the healthiest of the four types of fats.

The bad fats cause weight gain, clogged arteries, and a myriad of other negative health consequences. But the good fats support brain function, healthy skin, better mood, and so much more! (Source)

The different types of fats also affect our cholesterol levels differently. Bad fats raise bad cholesterol in our blood while good fats reduce bad cholesterol. And while you probably already knew that high cholesterol is a bad thing, I want to make sure you understand why so you fully comprehend the effects bad fats have on your overall health.

Let’s take a brief step away from the dietary fat conversation to talk about cholesterol, okay?

What’s up with cholesterol?

Cholesterol is a waxy, fat-like substance that’s found in all the cells in your body. Your body needs cholesterol to function properly. In fact, cholesterol helps your body make hormones, vitamin D, and bile. (Source) It’s also a building block for human tissues. (Source)

Cholesterol is pretty important, but problems arise when you get too much of it. You see, there are good and bad types of cholesterol.

• HDL (high-density lipoproteins) cholesterol is the good kind because it carries the bad cholesterol back to your liver to be eliminated from your body.
• LDL (low-density lipoproteins) cholesterol is the bad kind because too much of it can lead to plaque accumulation in your arteries. (Source 1, Source 2)

You want to keep the bad LDL levels low and the good HDL levels high. If the balance tips the other way and you have more of the bad LDL cholesterol than the good HDL cholesterol, you’re at risk of having plaque buildup in your arteries, which can cause even more health consequences such as narrowed arteries, heart attack, and stroke. (Source)

So how do you keep your cholesterol levels in check so you have more of the good kind than the bad kind?

To answer that, you need to know where people normally get their cholesterol.

First, your body makes its own cholesterol. In fact, your body makes all the cholesterol it needs! You absolutely do not need to get any cholesterol from your food in order to have enough for your body to function properly.

The body uses cholesterol for physiological and structural functions but makes more than enough for these purposes. Therefore, people do not need to obtain cholesterol through foods.

– 2015-2020 Dietary Guidelines for Americans

The second way you get cholesterol is through certain foods you eat. Animal products, to be exact.

Dietary cholesterol is found only in animal foods such as egg yolk, dairy products, shellfish, meats, and poultry.

– 2015-2020 Dietary Guidelines for Americans

Unfortunately, most of those animal products (excluding eggs and some shellfish, source) also contain the bad kind of fat. Remember what bad fat does to your cholesterol levels? It raises the bad LDL cholesterol. So not only are you getting extra cholesterol from those animal foods, but you’re also getting the bad fats that raise your bad LDL cholesterol even further.

So to keep your cholesterol levels in check, you can take a two-pronged approach of 1) avoiding or limiting the foods that contribute both dietary cholesterol and bad fats while 2) consuming more of the foods that contribute good fats. (Source)

In other words? Replace those bad fats with good fats. When you do that, you’ll naturally lower the bad LDL levels so the good HDL levels can shine.

Do we need fat in our diet?

You might be wondering whether we need fat in our diet given the conversation we just had about cholesterol.

In short, yes!

But the caveat is that we need good fats in our diet.

Good fats:

• Give us energy
• Support healthy skin
• Protect against memory loss
• Ease joint pain
• Help us absorb important fat-soluble vitamins A, D, E, and K

And so much more! (Source 1, Source 2)

So the goal is to consume good fats while minimizing or eliminating bad fats.

But how do you know which fats are good and which fats are bad? I’m so glad you asked!

Let’s talk about each of the different types of fats in more detail so you know what they are, where they’re found, what they do in the body, and why you should avoid or consume them.

Everything You Need to Know About the Bad Fats

Let’s start with the bad fats since those are running rampant in the standard American diet.

What are the bad fats?

Bad fats are easy to spot since they tend to be solid at room temperature. Think butter, cooled bacon grease, margarine, and shortening.

The bad fats are:

• Saturated fats
• Trans fats

Saturated Fats

What They Are

According to the American Heart Association, “Saturated fats are simply fat molecules that have no double bonds between carbon molecules because they are saturated with hydrogen molecules.”

Where They’re Found

Saturated fats are mostly found in animal foods such as meat and dairy products.

Here are some examples of animal foods with saturated fat:

• Beef
• Bacon
• Pork
• Sausage
• Lamb
• Chicken skin
• Whole and 2% milk
• Butter
• Lard
• Cheese
• Cream
• Ice cream

Given the most popular foods we eat here in America, the main sources of saturated fats in the standard American diet are mixed dishes made of meat and/or cheese. (Source)

Here are some examples of typical American dishes that contain saturated fat:

• Burgers
• Sandwiches
• Tacos
• Pizza
• Rice/pasta/grain dishes
• Meat/poultry/seafood dishes

Saturated fats are also found in certain tropical plant-based oils—coconut oil, palm oil, and palm kernel oil, to be exact. That’s why these oils are solid at room temperature.

The interesting thing to note is that while those tropical oils do have saturated fat in them, they do NOT contain cholesterol. Remember that dietary cholesterol is only found in animal products. (Source)

What They Do in the Body

Saturated fats raise bad LDL cholesterol in the blood, which can cause blockages to form in the heart and other parts of the body. That’s why saturated fats increase the risk of heart disease and stroke.

Saturated fats are also associated with:

• Increased total cholesterol
• Insulin resistance
• Type 2 diabetes

(Source 1, Source 2, Source 3)

Why You Should Avoid Saturated Fats

It’s pretty clear that saturated fats aren’t good for you and that it’s best to avoid them as much as possible, but here is another interesting point to note about saturated fats:

The human body uses some saturated fats for physiological and structural functions, but it makes more than enough to meet those needs. Individuals 2 years and older therefore have no dietary requirement for saturated fats.

– 2015-2020 Dietary Guidelines for Americans

Trans fats

What They Are

Trans fats come in two forms: naturally-occurring and artificially-made trans fats.

The naturally-occurring kind come from some ruminant animals such as cattle and sheep. Artificial trans fats are made by adding hydrogen to liquid vegetable oils to make them more solid. (Source)

Where They’re Found

Small amounts of trans fats are present in certain meat and dairy products made from ruminant animals. (Source)

Here are some examples of foods with naturally-occuring trans fats:

• Beef
• Lamb
• Butterfat

However, the main source of trans fats in the American diet is from processed foods such as commercially-made baked goods, packaged snack foods, fried foods, and frozen dinners. Foods that contain hydrogenated or partially hydrogenated oils, even if they claim to be trans fat-free, contain trans fat. (Source 1, Source 2)

Here are some examples of processed foods that contain artificially-made trans fats:

• Cakes
• Pastries
• Cookies
• Muffins
• Doughnuts
• Pie crusts
• Biscuits
• Crackers
• Microwave popcorn
• Chips
• Frozen pizza
• Pizza dough
• French fries
• Chicken nuggets
• Margarine
• Vegetable shortening
• Coffee creamer

(Source 1, Source 2, Source 3)

What They Do in the Body

This excerpt from an article published by Harvard Health clearly explains what trans fats do in the body:

Eating foods rich in trans fats increases the amount of harmful LDL cholesterol in the bloodstream and reduces the amount of beneficial HDL cholesterol. Trans fats create inflammation, which is linked to heart disease, stroke, diabetes, and other chronic conditions. They contribute to insulin resistance, which increases the risk of developing type 2 diabetes. Even small amounts of trans fats can harm health: for every 2% of calories from trans fat consumed daily, the risk of heart disease rises by 23%.

– The truth about fats: the good, the bad, and the in-between

Why You Should Avoid Trans Fats

As if the grim outlook from the Harvard article weren’t enough, the FDA determined that partially hydrogenated oils (which is the main source of artificially-made trans fats), are no longer generally recognized as safe (GRAS) for any use in human food. (Source)

How to Minimize the Bad Fats in Your Diet

If you read over the lists of foods that contain saturated and trans fats, then you might be wondering how on earth you can minimize the bad fats in your diet, especially since the standard American diet mainly consists of those very foods.

I get it. It’s a tough pill to swallow, and nobody said choosing a healthier way would be easy.

However, if you’re interested in minimizing the bad fats in your diet, then here are some actionable steps to take:

• Avoid or strictly limit your intake of animal foods such as meat, seafood, poultry, and dairy products
• Avoid or strictly limit your intake of processed foods such as prepackaged snacks, commercially-made desserts, frozen meals, and fried foods
• Eat more fresh fruit, fresh vegetables, whole grains, legumes (beans, peas, and lentils), nuts, and seeds
• Make your meals at home using fresh, minimally-processed ingredients

Everything You Need to Know About the Good Fats

Now let’s switch gears and talk about the good fats.

What are good fats?

Good fats are unsaturated, and they tend to be liquid at room temperature. We call these good fats “oils.” Refined oils like olive oil are easy to spot, but oils in their natural state are less obvious since they’re found inside foods such as avocados, olives, nuts, and certain fish.

The good fats are:

• Monounsaturated fats (MUFAs)
• Polyunsaturated fats (PUFAs)

Monounsaturated fats

What They Are

According to the American Heart Association, “Monounsaturated fats are simply fat molecules that have one unsaturated carbon bond in the molecule, this is also called a double bond. Oils that contain monounsaturated fats are typically liquid at room temperature but start to turn solid when chilled.”

Where They’re Found

Monounsaturated fats are found in greatest amounts in plants. (Source)

Here are some examples of plant foods high in monounsaturated fats:

• Liquid vegetable oils such as olive, sunflower, peanut, safflower, and sesame oils
• Avocados
• Nuts
• Seeds
• Peanut butter

What They Do in the Body

Monounsaturated fats can help lower bad LDL cholesterol levels in the blood, which in turn lowers the risk of heart disease and stroke. (Source)

Monounsaturated fats also:

• Increase good HDL cholesterol in the blood (Source)
• Supply vitamin E, which is an antioxidant vitamin (Source)

Why You Should Consume Monounsaturated Fats

Since your body needs good fats to function properly, it’s a good idea to replace unhealthy saturated fats and trans fats with healthy monounsaturated fats.

Polyunsaturated fats

What They Are

Polyunsaturated fats are fat molecules that have more than one unsaturated carbon bond in the molecule. Like monounsaturated fats, polyunsaturated fats are usually liquid at room temperature. (Source)

Polyunsaturated fats are unique in that they provide essential fats that your body needs but can’t produce itself, namely omega-3 and omega-6 fatty acids. (Source)

Where They’re Found

Polyunsaturated fats are found in plants and certain fish.

Here are some examples of foods high in polyunsaturated fats, specifically ones high in omega-3 fatty acids:

• Soybean oil
• Walnuts
• Flaxseed
• Fatty fish such as salmon, tuna, mackerel, and sardines

(Source)

Here are some examples of foods high in polyunsaturated fats, specifically ones high in omega-6 fatty acids:

• Liquid vegetable oils such as soybean, corn, sunflower, walnut, and safflower oils

(Source)

Other good sources of polyunsaturated fats include:

• Seeds such as sunflower, sesame, and pumpkin seeds
• Soybeans and tofu
• Fish oil supplements

(Source 1, Source 2)

What They Do in the Body

Polyunsaturated fats serve a variety of functions. According to an article published by Harvard Health, polyunsaturated fats lower bad LDL cholesterol in the blood, which can lower your risk for heart disease and stroke.

Polyunsaturated fats also:

• Help with blood clotting, muscle movement, and inflammation
• Are used to build cell membranes and the covering of nerves
• Lower triglycerides

Why You Should Consume Polyunsaturated Fats

Omega-3 and omega-6 fatty acids are essential for your body to function properly, so it’s important that you regularly eat foods rich in polyunsaturated fats.

Also, this quote from the 2015-2020 Dietary Guidelines for Americans emphasizes the relationship between polyunsaturated fats and cardiovascular disease (CVD):

Strong and consistent evidence shows that replacing saturated fats with polyunsaturated fats is associated with a reduced risk of CVD events (heart attacks) and CVD-related deaths.

– 2015-2020 Dietary Guidelines for Americans

I don’t know about you, but reducing the risk of heart attack and cardiovascular disease-related death is a pretty convincing reason to make the switch to polyunsaturated fats!

How to Get More Good Fats in Your Diet

It’s fairly easy to get more monounsaturated and polyunsaturated fats in your diet, especially if you’re already a big fan of whole plant foods. Remember that these good fats are present in nuts, seeds, nut butters, olives, avocados, and oils made from plants. They’re also found in fatty fish such as salmon and tuna.

Here are some actionable ways to include more good fats in your diet:

• Eat a variety of whole plant sources of fats each day
• Eat fatty fish on occasion (unless you’re vegan, vegetarian, or 100% whole food plant-based)
• Replace butter or margarine with extra virgin olive oil when cooking (unless you’re 100% whole food plant-based)
• Use nut butter instead of butter or margarine on your toast
• Add mashed avocado to your sandwich instead of mayo
• Make guacamole as a dip for vegetables or tortilla chips
• Top your salad with cubed avocado, nuts, and/or seeds
• Toss in a tablespoon of ground flaxseed to your morning smoothie
• Snack on olives
• Snack on homemade trail mix made with nuts, seeds, and dried fruit

Related: 9 Sources of Healthy Plant-Based Fats You Should Always Have in Your Kitchen

Is Oil Really A Healthy Source of Good Fats?

I do want to include some additional thoughts on refined oils, even the ones that are high in good monounsaturated and polyunsaturated fats.

To be clear, the oils I’m referring to here are the kind you buy in a bottle, like olive oil or canola oil. These are refined oils, also called “added oils.” I am NOT referring to oils found in their natural state, such as the oils naturally present in avocados or nuts.

Many notable plant-based doctors suggest avoiding refined oils as much as possible since oils are highly processed and have some adverse health effects when you consume them. All oils, even “good” ones like olive oil, impair endothelial function to various degrees. (Source)

Beyond that, oils are nutritionally deficient. While you do get omega-3 and omega-6 fatty acids from oil, refined oils are stripped of the fiber, vitamins, minerals, and phytochemical compounds that you’d normally get by eating the whole food (i.e. eating the olive instead of the olive oil, or eating the walnut instead of the walnut oil). (Source)

Also, oil is calorically dense. Fat supplies more than twice as many calories per gram when compared to carbohydrates and proteins. Carbohydrates and proteins each have 4 calories per gram, while fat has 9 calories per gram. (Source)

Since oil is pure fat, even a small amount of it adds a significant amount of calories. In fact, you get about 120-130 calories for every tablespoon of oil you consume. (Source) That’s a lot of calories for a nutritionally-deficient food substance that does nothing to make you feel full.

These are all good reasons to avoid added oil as much as possible, and swapping out refined oils in favor of the whole plant food will allow you to get plenty of good fats along with other important nutrients like fiber, vitamins, and minerals.

How to Reduce Oil in Your Diet

If you’d like to reduce the amount of added oil in your diet, here are some actionable tips to try:

• Bake or steam your vegetables instead of frying them in oil
• Replace oil with applesauce, mashed banana, or nut butter in baking recipes
• Use a small amount of water or vegetable broth instead of oil to sauté your food
• Top your salads with vinegar, tahini, or mashed avocado instead of oil or oil-based dressings
• Make your own oil-free fries at home instead of buying fast food or frozen fries
• Air-pop your popcorn instead of making microwave popcorn

Special Considerations for Dietary Fat If You’re Trying to Lose Weight

We know dietary fat is important for your health, but what if you’re trying to lose weight?

As I mentioned before, fat is the most concentrated source of calories. At 9 calories per gram, it has more than twice as many calories per gram as carbohydrates and proteins (they only have 4 calories per gram each).

Since you don’t want to consume unnecessary calories when you’re trying to lose weight, you’ll need to monitor your intake of dietary fat, both from added oils and whole food sources of dietary fat.

Added Oils

Since oil is pure fat, you’ll want to be especially vigilant about added oils, even the so-called “good” oils like olive oil.

Oils pack a serious calorie punch (a whopping 120-130 calories per tablespoon) without any of the fiber that contributes to satiety, so they’re basically a waste of calories when you’re trying to lose weight. Translation? You eat the calories without feeling full.

With that being said, you’ll want to cut out as many sources of added oil as possible. This means using cooking methods that don’t require oil, skipping the oily dressings on your salad, and scouring the ingredient list on food labels for hidden sources of added oil.

Whole Food Sources of Dietary Fat

Whole food sources of good fats such as avocados, nuts, and seeds, are more calorically-dense than other foods that don’t have as much fat in them, such as fruit, vegetables, whole grains, and legumes.

For example, you’ll consume more calories when you eat a handful of nuts than when you eat a handful of berries because the nuts have more fat in them than the berries.

It makes sense, right? If a certain food is a good source of good fat, then it literally means that food has a significant amount of fat in it.

Of course, whole food sources of dietary fat aren’t as calorically-dense as pure oil, but it’s still important to recognize the higher fat content when you’re trying to lose weight.

So what does this mean your plate should look like at mealtime?

When preparing meals, you’ll want to limit your intake of those calorically-dense foods and instead fill your plate with foods that are lower in calorie density such as fruit, vegetables, whole grains, and legumes.

Likewise, you’ll want to snack on foods that are lower in calories such as fruit or vegetables instead of chowing down on a bag of walnuts.

You can still have those good sources of good fats, but it’s important to limit your intake so you don’t consume excess calories.

Final Thoughts on Dietary Fats

Let’s end our conversation about dietary fats with a quick recap, shall we?

The bad fats are:

• Saturated fats
• Trans fats

Saturated fats are found in animal products such as meat and dairy products, while trans fats are mostly found in processed foods such as prepackaged snacks, commercial pastries, frozen dinners, and fried foods. Both of these types of fats increase bad LDL cholesterol, which can cause heart disease, stroke, and Type 2 diabetes.

The good fats are:

• Monounsaturated fats
• Polyunsaturated fats

Monounsaturated fats and polyunsaturated fats are mostly found in plant foods. Think nuts, seeds, olives, avocados, and oils made from plants. They’re also found in fatty fish like salmon and tuna. These good kinds of fats decrease bad LDL cholesterol and help prevent heart disease and stroke while supplying the fat our bodies need to function properly. Polyunsaturated fats are also a source of two essential fatty acids that our bodies need but can’t produce on their own: omega-3 and omega-6 fatty acids.

While refined oils are technically a good source of monounsaturated and polyunsaturated fats, they might not be the best use of your allotted daily calories. Oils contain about 120-130 calories per tablespoon but without any of the components that contribute to satiety. This means you eat the calories without feeling full.

Oils are also nutritionally-deficient since they’re stripped of the fiber, vitamins, and minerals that are otherwise present in the whole food form.

The best way to get good dietary fat is through whole food sources. When you eat the real thing (i.e. the olive, not the olive oil), you get Mother Nature’s original, nutrient-dense package loaded with healthy monounsaturated and polyunsaturated fats, fiber, vitamins, and minerals.

But if you need to lose weight, it’s important to remember that even those whole food sources of good fats are more calorically-dense than other foods such as fruit, vegetables, whole grains, and legumes. Cutting out oil and limiting your intake of high-fat plant foods will allow you to get the dietary fat you need without consuming excess calories.

Other Healthy Lifestyle Articles You May Enjoy

• 9 Sources of Healthy Plant-Based Fats You Should Always Have in Your Kitchen
• Why We Transitioned to a Mostly Plant-based Lifestyle
• The Whole Food, Plant-Based Diet Explained
• 5 Crucial Things I Did to Ditch My Chronic IBS for Good
• 12 Healthy Habits You Can Start Today

Did I answer all of your questions about dietary fat? If not, leave me a comment below with your question and I’ll answer it!

Want to remember this? Save it to your favorite Pinterest board by clicking the images below!

The Complete Guide to Dietary Fats (the simple version!)