You might eat lots of fat.
You might not eat much fat at all.
Regardless, you likely have questions about it.
In this post, we’ll cover the basics about dietary fats and what kinds you may or may not want to eat (and how much).
If you have any questions after reading, let me know in the comments 🙂
What are fats?
Dietary fats belong to a class of fatty, waxy, oily molecules that do not dissolve in water called “lipids” (1).
The fats we eat are a type of lipid called triglycerides.
A triglycerides comprises a glycerol backbone with three fatty acids attached to it.
These fatty acids are chains of carbon and hydrogen, classified by their length and degree of saturation, or number of double bonds between carbons.
Saturated fatty acids have no double bonds, monounsaturated fatty acids have one double bond, and polyunsaturated fatty acids have two or more double bonds.
Trans fatty acids have double bonds, too, but they’re named according to the configuration of their double bonds.
Their “trans” configuration makes them more similar to saturated fatty acids than other “cis” unsaturated fatty acids.
Fatty acids can also be categorized by their chain length:
- short chain (three to six carbons)
- medium chain (eight to 14 carbons)
- long chain (16 or more carbons)
What role do fats play in the body?
Fats, and lipids in general, are critical to a variety of processes going on throughout our bodies (2).
For example, we use them for hormone production, cell membrane synthesis, and brain and nervous system structure and function.
Fats help with the absorption of fat-soluble nutrients like vitamins A, D, E, and K and phytonutrients.
They serve as a source of essential omega-3 and omega-6 polyunsaturated fatty acids.
Of course, as you likely already know, we use fat as a means for storing energy in adipose tissue.
That said, different types of fat may have different effects on our health.
What are healthy fats?
When it comes to any food, “healthy” is subjective.
That is, it depends on each of our individual needs, preferences, and goals.
However, there’s plenty of research to look at to get a feel for general trends and effects.
At the very least, this can serve as a starting point for us to use to get started dialing things in.
Let’s look how each of the fatty acid types we discussed earlier might affect our health.
Monounsaturated fatty acids
One type of fatty acid that you might want to prioritize in your diet is monounsaturated fatty acids (MUFAs).
You’ll find MUFAs in olives, avocados, nuts, and some animal sources like beef and pork.
Omega-3 polyunsaturated fatty acids
Another type of fatty acid that appears to offer health benefits are omega-3 polyunsaturated fatty acids (PUFAs).
What are unhealthy fats?
You’ve probably already heard or been told to steer clear of saturated fats.
On the other hand, you might also have been told that they’re totally benign.
We’ll get to saturated fats in a bit, but for now we’re going to shift our attention elsewhere.
Pretty much the only type of fat universally recognized as harmful are those rich in artificial trans fatty acids.
Artificial trans fatty acids
You’ll mainly find artificial trans fatty acids in hydrogenated vegetable oils used in baked goods, margarine, and other processed oils and spreads.
That said, some trans fatty acids occur naturally in fats from ruminants like sheep and cows.
These natural trans fatty acids don’t appear to promote the same adverse health outcomes as artificial trans fatty acids (13).
To the contrary, some might actually be quite beneficial.
For example, one called conjugated linoleic acid (CLA) appears to promote cardiovascular health (14).
Fats we’re just not sure about
For other types of fats, it’s not quite clear whether they’re beneficial or detrimental to our health.
Omega-6 polyunsaturated fatty acids
Omega-6 PUFAs are found in nuts, seeds, and vegetable oils like sunflower, corn, cottonseed, and soybean oils.
However, it’s not clear whether high omega-6, a high omega-6 relative to omega-3, or low omega-3 intake drives these effects.
There’s evidence suggesting omega-6 PUFAs aren’t inherently problematic, but may be an issue when used for cooking.
For instance, heated vegetable oils might oxidize, promoting inflammation that may contribute to the development of conditions like atherosclerosis (18).
Instead of cooking with vegetable oils, you might consider cooking with more stable extra virgin olive oil, coconut oil, avocado oil, or other high-oleic oils (19).
Saturated fatty acids
Saturated fatty acids usually come up during discussions about butter or meat.
However, you can also find saturated fatty acids in plant fats like coconut and palm oil.
You’ll probably want to pay attention to how different types of fats affect you personally.
Consider keeping an eye on your blood lipids and other health markers with the help of a knowledgeable physician.
How much fat should I eat?
Figuring out how much to eat of any food or nutrient isn’t always easy.
However, there are a few general guidelines you might consider as a starting point.
You’ll then get your biggest bang for your buck by dialing things up and down to find what works best for you.
First, though, let’s cover some basic ideas.
Fats vs. carbs
You’ll probably want to get at least 20 – 35% of your calories from fat (22).
This should help make sure you’re getting enough essential fatty acids and fat-soluble vitamins.
Beyond that, though, you likely have some wriggle room.
There may be a slight advantage to low-fat diets over low-carb diets, in terms of body composition.
For example, a 2018 meta-analysis of 32 studies with over 500 total participants found that low-fat diets facilitated greater energy expenditure and fat loss than low-carb diets (23).
That said, the differences in energy expenditure and fat loss were pretty slim.
The energy expenditure advantage was 26 kcals/day and the fat loss advantage was 16 g/day.
Furthermore, these were controlled-feeding studies with calories and protein equal across study arms.
In the real world, we all have different needs, preferences, and goals that play a role in which eating habits work best for us.
If you’re looking to dial in your diet, though, there’s one step you can take first to make the rest of the process infinitely easier.
Prioritize minimally-processed foods
Participants in a 2018 randomized clinical trial saw similar improvements in weight and health, regardless of whether they restricted carbs or fats (24).
Those who were most successful prioritized minimally-processed foods and found an approach they could stick to consistently.
Similarly, in a 2019 trial, participants freely eating ultra-processed foods consumed 500 calories more per day than those freely eating unprocessed foods with the same nutrient profile (25).
Finally, a 2020 study of 37,000 people concluded that food quality appears to be a more important factor in mortality risk than relative fat or carbohydrate content (26).
So, you might start by prioritizing nutrient dense, minimally processed sources of fat.
This includes animal sources like beef, lamb, eggs, nuts, seeds, olives, avocados, fatty fish a few times a week, and quality oils.
From there, start dialing your fat intake up and down to see how you feel.
Of course, it’s not always easy to tell how much fat you’re getting.
After all, many foods (like eggs, meat, dairy, and nuts) often include fat along with protein and/or carbs.
Furthermore, most of us aren’t very good at estimating or remembering how much or what we eat (27).
Consider tracking your food in a tool like Cronometer, and perhaps even weighing and measuring portions.
If you don’t like the idea of all this detailed measuring and recording, that’s totally cool.
However, you might consider it as a temporary effort to get a feel for which foods offer which nutrients.
That is, you might see tracking and recording similar to training wheels when learning to ride a bike.
What to do now
Experiment a bit with different relative levels of fat intake to find what works best for you.
If you’re eating leaner cuts of meat, or very little fatty fish or eggs, you might want to add a thumb-sized serving or two of nuts, olives, avocado, or healthy oil to each meal.
If, on the other hand, you’re eating a lot of fattier cuts of meat, eggs, and fish, you might not need or want to add any nuts, olives, avocado, or healthy oils.
As you dial up your fats, you’ll generally want to dial down your carbohydrates, and vice versa.
You might feel better with more carbohydrates and less fat.
On the other hand, you might feel better with more fat and less carbohydrates.
Of course, you might feel better with an even balance of the two.
Explore different sources of fat to see which ones you enjoy eating.
Keep an eye also on how different fatty foods make you feel.
For example, do specific fats affect your appetite, heart rate, or even factors like swelling, bloating, or mental focus?
You might find a food journal to record your observations helpful in figuring this all out.
Only you can determine which fats and what amount work best for you.
This may not be an easy process.
It may take some time, effort, and patience.
You’re worth it, though.
You’ve got this.