Ultimate Guide to Fat: the good, the bad, and everything in between

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Everything you need to know about healthy fats, fats to avoid, and which fats are right for your body.

The confusion about fat is probably one of the most notorious topics in nutrition. Until a few years ago, fat was vilified by just about everyone - including professional health organizations and health care professionals - as the root cause of heart disease and obesity.

More recently, the dialog around fat has shifted and we are embracing fat like never before as a key nutrient for heart health, hormone balancing, and even weight loss.

Should you jump on the fat bandwagon or is this just another fad? Keep reading to find out what types of fat you should eat, which fats you should avoid, and which fats are right for your specific body.

What is fat exactly?

Fat is a key macronutrient that supports our health in many ways. There are three main categories of fats (which are also known as fatty acids): saturated, monounsaturated, and polyunsaturated fats.

Each of these fats has a different chemical structure which give it different properties and functions in the body. Within each category of fat, there are several different types of fatty acids. For example arachidonic acid and gamma-linolenic acid (GLA) are different types of polyunsaturated fats.

One of the most important things to keep in mind about fat is that all plant and animal fats contain a combination of different types of fatty acids.

For example, lard considered a saturated fat, but it actually contains more monounsaturated fat (45%) than saturated fat (44%). In fact, most of the monounsaturated fat found in lard is oleic acid, which is the same fatty acid that gives olive oil its heart health benefits! Likewise, olive oil is the most well known monounsaturated fat, but it still contains 14% saturated fat.

This helps to explain why so much of the research on fat has conflicting results.

Why you need to eat fat

Fats are one of our primary energy sources and we must consume them in order to survive. Over the last few years the importance of fat has become so evident that even the 2015 US Dietary Guidelines for Americans eliminated the upper limit once placed on fat intake.

Fats insulates our organs and serve as structural components of our cells. They support immune function, help to regulate our body temperature, maintain healthy skin, hair and nails, and help us absorb essential fat-soluble vitamins like vitamin A, D, E, and K.

Some fats, like omega-3 fatty acids and monounsaturated fats fight inflammation, support heart health, and are also extremely important for brain health. Other fats, like cholesterol serve as a building block for creating hormones.

The jury is out…eating fat is more than just a fad, it’s here to stay.

What are the best fats for your health?

Generally speaking, "good fats" are fats that support the cardiovascular system, balance hormones, and fight inflammation. The trouble is that not everyone agrees which fats are good and which fats are bad. Here's a breakdown of the current research on certain fats.

MONOUNSATURATED FATS

Pretty much everyone can agree that monounsaturated fats are “good fats,” especially when it comes to heart health.

Monounsaturated fats have one (“mono”) point in their carbon chain that is “unsaturated” with hydrogen, causing a double carbon-to-carbon bond.

I know the chemistry can be a bit intimidating, but the key thing to to remember is - the chemical structure of monounsaturated fats makes them liquid at room temperature and usually solid when refrigerated. They are also moderately sensitive to heat and light, which is why extra virgin olive oil is usually bottled in darker bottles and smokes pretty easily with high heat cooking.

Foods that contain mostly monounsaturated fats are:

hazelnuts
cashews
and a few animal fats like poultry and pork.

olives and olive oil
avocado and avocado oil
macadamia nuts
almonds

Monounsaturated fats reduce LDL cholesterol (aka "bad cholesterol") and triglycerides, and increase HDL (aka "good cholesterol"), making them ideal for heart health (1).

They also reduce oxidation and inflammation, lower blood pressure, and improve insulin sensitivity (1, 2, 3).

OMEGA-3 POLYUNSATURATED FATS

Most experts also agree that omega-3 fatty acids are "good fats."

Omega-3s are an essential fat that belong to a group of fats called polyunsaturated fats, or PUFAs. PUFAs have multiple double bonds along their carbon chain, which allows them to attach to and deactivate harmful compounds in the body like free radicals.

Their chemical structure also makes them liquid at both room and refrigerated temperatures. They are very sensitive to light and heat, and prone to oxidation and rancidity. As a result, they are best kept refrigerated and should not be used for cooking.

There are actually several types of omega-3 fatty acids, but the most important ones are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). These omega-3s are critical for the proper functioning of our immune, inflammatory, cardiovascular, and nervous systems. We cannot synthesize omega-3s in our body and need to get them from our diet to meet our needs.

Omega-3s have been well researched for their heart and brain health benefits. Several studies have found that eating omega-3 fatty acids from fish decreases the risk for heart disease and sudden cardiac death (4). Research has also shown that omega-3s lower triglycerides and blood pressure (5, 6).

Studies linking omega-3s to other health benefits, such as decreased risk for dementia and depression are inconclusive, but omega-3s remain a key nutrient for fighting inflammation associated with several diseases.

Recommended reading: Can Omega-3s Help your Depression

The best source of omega-3 fatty acids are cold-water, fatty fish like salmon, mackerel, herring, sardines, anchovies, and bass, as well as shellfish like oysters and mussels.

Plant-based sources of omega-3 like walnuts, flax and chia seeds need to get converted to the active forms of omega-3 (DHA and EPA) and may not be sufficient to meet our needs exclusively.

What are the worst fats for your health?

TRANS FATS

Trans fats are one of the few fats that are universally considered as “bad fats.” There are two main types of trans fats, artificial or man-made trans fats, and naturally occurring trans fats.

Artificial trans fats are usually made by adding hydrogen to liquid vegetable oils to create a fat that is solid at room temperature. They are commonly referred to as hydrogenated fats on food labels, and can be found in many processed foods, including:

Crackers, cookies, cakes, frozen pies, and other baked goods
Snack foods (such as microwave popcorn)
Frozen pizza
Fast-food
Vegetable shortenings and some stick margarines
Coffee creamer
Refrigerated dough products
Ready-to-use frostings

Artificial trans fats have been shown to increase the risk of cancer, heart disease, obesity, and other inflammatory conditions—even at relatively low doses (7).

However, naturally occurring trans fats like conjugated linoleic acid (CLA), which is found in small amounts of grass-fed animal meat and dairy products has actually been associated with a lower risk of heart disease, improved glucose tolerance, reduced cancer risk, and may even help promote weight loss (8, 9, 10, 11). We need more research to understand how naturally occurring trans fats influence our health, but for now it seems like we can take then out of the “bad fat” category.

What about omega-6, cholesterol, and saturated fat?

These are the most controversial of the fats, and their benefit vs. harm usually depends on the individual, the type and amount consumed, and the diet overall.

OMEGA-6 POLYUNSATURATED FATS

Omega-6 is a polyunsaturated fat also known a linoleic acid. It is essential to human health, but too much of this fatty acid can actually promote inflammation. Food sources of omega-6 include industrial seed oils like canola, peanut, soybean, and sunflower oil. They are also found in smaller amounts in nuts and seeds.

When eating foods with omega-6 fatty acids, it's important to make sure you are also getting enough DHA and EPA to minimize the pro-inflammatory effects of omega-6.

To do this, I recommend avoiding vegetable oils (canola, soy, peanut, etc.), which are the most concentrated source of omega-6 fatty acids, and meeting your needs through whole foods like nuts, seeds and avocado.

CHOLESTEROL

The 30 plus years of recommendations to restrict cholesterol were eliminated from the US Dietary Guidelines for Americans in 2015. Some people are genetically predisposed to be more sensitive to cholesterol, but for the vast majority of people, cholesterol in our diet does not impact cholesterol in our blood.

We actually make cholesterol in our body because we have a very high demand for it. Cholesterol serves as the building block for many of our hormones, vitamin D, and is a key structural component of our cells.

Bottom line, cholesterol is a "good fat" for most people, but can increase LDL cholesterol for a small percentage of the population who are genetically disposed to hyper-absorb cholesterol in the diet. We can at least take cholesterol out of the "bad fat" category and put it in the “it depends” category.

SATURATED FATS

Saturated fats (SF) are probably the most controversial of all the fats. Their carbon chain is completely saturated with hydrogen, which makes SFs solid at room temperature, not prone to oxidation, and great for high heat cooking.

SFs were considered "bad fats" for decades because of their ability to increase LDL cholesterol. However, more recent research has debunked previous studies, and found that saturated fat may not be so harmful after all (12).

SFs are categorized based on their length - long, medium, and short chain. Long chain SFs are found mostly in milk products and the meat of cows and sheep. We mostly store fat in our bodies in the from of long chain SFs. Interestingly, one long-chain SF, stearic acid, has actually be shown to lower LDL cholesterol (13).

Medium chain SFs (aka MCTs) like lauric and caprylic acid are primarily found in coconut milk and breast milk. These fats are absorbed faster than long-chain saturated fats and serve as a good, quick source of energy. Lauric acid is also a potent anti-fungal/bacterial/viral agent. Medium chain saturated fats have also been shown to enhance fat burning (14).

Short chain saturated fats like butyric, propionic, and acetic acid can be found in grass-fed butter and ghee. Our gut microbiome also makes short chain fatty acids that serve as fuel for the cells of our colon and also help with cell signaling.

As you can see there are actually quite a few benefits of saturated fats. More recent research has found that similar to the finding on dietary cholesterol, saturated fat may only be harmful to a subset of people who are more likely to be sensitive to effects of dietary saturated fat on LDL cholesterol.

The issue is even more complicated, because the vast majority of whole foods that contain saturated fat, also contain other fats like monounsaturated and polyunsaturated fats. So when we consume whole foods that are higher in saturated fat, like full fat dairy products, we are also consuming "good fats" which might balance out any risks associated with eating saturated fat (15).

Also…certain saturated fats increase both LDL and HDL cholesterol, which likely results in more of a neutral effect on cholesterol levels and overall heart disease risk.

And finally…newer research suggests that LDL-C may not be the best indicator for determining cardiovascular disease risk, but rather the number of LDL particles (LDL-P) might be a more important marker to measure.

It's all very confusing and we definitely don't have answers yet, but I believe we can take saturated fat out of the "bad fat" category and put it in the “it depends” category and even the "good fats" category depending on the person.

Bottom Line on Fats

Fats are necessary for sustaining life and have several functions in our body beyond energy storage.
Fat does have more calories per gram compared to protein and carbohydrates and can contribute to weight gain if eaten in excess of energy needs.
Fat helps you to feel full and can be an important part of managing your appetite.
Eating fatty fish (versus supplementing with fish oil) is the best way to meet your needs for omega-3s and prevent heart disease.
Avoid industrial seed oils like canola oil, and increase your intake of DHA and EPA to minimize the pro-inflammatory effects of omega-6 fats.
If you have familial hypercholesterolemia be mindful of your saturated fat and cholesterol intake. The majority of other people can enjoy these fats without them having a negative effect on blood lipids. Always get your labs tested to confirm how dietary cholesterol and saturated fat effect your markers for cardiovascular disease risk.