Of all the Macronutrients, Fat has been given a bad reputation. But is this bad reputation warranted? And if we should include fat in our diet, how much should we be eating?
Before we answer the question of how much fat, we need to understand what are fats, also known as lipids.
To begin with, we have monounsaturated fats. These tend to be seen in a positive light and can be found in foods such as olives, olive oil, avocados, avocado oil, macadamias, and other nuts/seeds, and more. As you can see above, MUFAs only have a Single Double Bond in their structure, hence the prefix Mono-.
Similar to MUFAs, Polyunsaturated Fatty Acids (or PUFAs) are typically known to be beneficial, as you can find them in foods such as chia seeds, fish oil, flaxseeds, walnuts and more. Omega-3 and Omega-6 Fatty Acids are PUFAs. Their chemical structure contains two or more double bonds. Both MUFAs and PUFAs are usually found in liquid form at room temperature, e.g. olive oil and avocado oil. This is because their chemical structure does not lend themselves well to bonding with one another.
Next, we have Saturated Fatty Acids. SFAs have been the most demonized of the fatty acids. These are fats that can often be found in animal sources of food, such as fatty beef, lamb, butter, and other whole fat dairy products. While animal foods are the most common source of SFAs you can still get SFAs from foods like coconut, palm oil, and dark chocolate. SFA’s chemical structure contains no double bonds, so all carbons (C) are saturated with hydrogens (H) and this inhibits other atoms like Oxygen (O) from binding to the hydrocarbons in the chain making SFAs more chemically stable. SFAs will typically be solid or semi-solid at room temperature. (Berardi, et al., 2016, pg. 195)
Lastly, there are Trans Fatty Acids. The name – trans – comes from their chemical configuration. Most naturally occurring unsaturated fatty acids are typically found in the cis configuration, which contains kinks or bends in its structure. A process called partial hydrogenation takes polyunsaturated fatty acids, which are less chemically stable; meaning they quickly oxidize and go rancid, and rearranges these polyunsaturated fatty acids into a trans form. This trans form is more chemically stable and has a similar linear structure as a saturated fatty acid. This process was created to allow these fats to be more shelf-stable and led to foods like margarine. (Gropper & Smith, 2013, pg. 138-139)
As a side-note on trans fats, there are naturally occurring trans fats and these are found in ruminant animals such as sheep and cows. I know what you’re thinking, you heard red meat was bad for you and this is probably one of the reasons why. The naturally occurring trans fat in ruminant animals is called Conjugated Linoleic Acid (CLA) and doesn’t appear to harm us. Rather, CLA may be beneficial.
After a quick lesson on the types of fatty acids; though we did not cover Omega-3 and Omega-6 fatty acids, we can dive into which of these fats should make up our diet.
What has been clearly illustrated in the nutrition literature is avoiding manmade trans fats (partially hydrogenated vegetable oils) and not the naturally occurring ones created by bacteria in the rumen of cows and/or sheep. Consuming partially hydrogenated vegetable oils increases your risk of many diseases (e.g. CVD, cancer and diabetes), which is why in 2015 the FDA determined these oils were no longer GRAS (Generally Recognized as Safe) and would be phasing them out of our food system.
Where there is more confusion is around saturated fats. I am sure you have been told, at one time or another, to limit your intake of SFA or increase your risk for cancer, heart disease, and diabetes. Then, when you look at which foods are high in saturated fat you realize they are primarily found in animal products, foods like meat, dairy, and eggs.
So, should you avoid them? Because the topic of saturated fat is one that is confusing and controversial, and I do not intend to take a deep dive in this article; instead, I will touch on those topics as time goes on and break them down into easier to digest pieces.
I want to provide some context into why nutrition and medical professionals are concerned with saturated fat. This has to do with how SFAs can affect our blood lipid markers, such as LDL, HDL, total cholesterol, and triglycerides, to name a few. By the way, cholesterol is another topic much controversy exists, so it will be covered similarly as Saturated Fat.
Typically, we want to see low-density lipoproteins (LDL) below a certain level, high-density lipoproteins (HDL) between a certain range, and total cholesterol and triglycerides below a certain level. What has been shown in some nutrition research is high intakes of SFAs result in undesirable changes to blood lipids.
Does this mean to avoid this food completely? No.
What is important to realize is that foods that contain SFAs also contain other fatty acids. For example, the fat in beef is ~46% MUFA, ~5% PUFA, ~46% SFA, and ~3% Trans fat (CLA). So when someone tells you red meat is bad because it is “high” in saturated fat; remember is contains other fats as well, not just saturated fats. If you are eating a diet that consists of whole, minimally-processed foods, that include red meat, and your blood lipid markers are within a healthy range, should you worry and completely cut it out? I don’t believe so.
What about foods like dairy: cheese, eggs, and milk? Interestingly, when you look at interventional studies with cheese, some experience improvements in blood lipid markers and a meta-analyses by Tong et al. found the consumption of cheese “is not significantly associated with risk of all-cause mortality”. As for eggs, people are often worried about cholesterol, however, in the most recent Dietary Guidelines for Americans, the USDA stated that cholesterol was no longer a nutrient of concern due to a lack of evidence. It may come as a surprise, but our body makes roughly 80% of the cholesterol it needs and the other 20% comes from our diet, so the dietary cholesterol we eat has a small effect on our cholesterol levels. As far as milk goes, a 2017 meta-analysis of prospective cohort studies looking at milk and dairy consumption found a neutral association of total, high, and low-fat dairy, milk, and yogurt with the risk of all-cause mortality. More recently, a 2019 meta-analysis found that a greater intake of total dairy has a beneficial association with mortality; however, there was an association with milk intake and higher CHD mortality.
Okay. Hopefully, you’re still with me!
We will finish up with monounsaturated fats and polyunsaturated fats.
The nutrition literature often associates health benefits with consuming foods high in MUFAs and PUFAs. They are associated with decreasing your risk for cardiovascular disease, Alzheimer’s and dementia while improving blood pressure, lowering fasting triglycerides, increasing HDL, and all-cause mortality.
One of the unfortunate outcomes of demonizing saturated fats was the substitution and increased consumption of oils high in polyunsaturated fatty acids. Oils such as corn, vegetable, soybean, peanut, grapeseed, sunflower, and safflower are all higher in PUFAs. Polyunsaturated fatty acids are not bad in and of themselves; however, if you can recall, these fats are highly susceptible to oxidation. An oxidized oil is a rancid oil, so if it exposed to high heat and/or air (oxygen) it goes through this process. (Gropper & Smith, 2013, pg. 138-139) This is why they created the process of partial hydrogenation, to protect these oils from going bad, but remember what that resulted in.
The oils like olive oil and avocado oil are better choices because they are higher in monounsaturated fats and have lesser amounts of polyunsaturated fatty acids; reducing the likelihood of them being oxidized. Additionally, the polyphenols that olive oil contains further protects the fatty acids from becoming oxidized.
I will list food sources of all the fatty acids you can include in your diet at the end.
At last, we are at how much fat we should eat!
You may not like the answer, but here it is:
Everyone has different goals and is at a different place with their health. With different health statuses, goals and dietary preferences come a unique amount of fat.
There was an interesting study that looked at two groups. One group was following a low carbohydrate/high-fat diet; while the other followed a high carbohydrate/low-fat diet. What did the study show?
A great place to start is looking back at what have you tried in the past. Specifically, what led to the greatest results and felt sustainable? I believe it is important to make changes to your habits and lifestyle that you can see yourself sustaining; rather than looking for quick fixes, only to end up where you started, or in an even worse situation.
Here are some examples of Macronutrient Ratios one can follow:
As you can see there are many possibilities and even more than what I am presenting to you. There continues to be more research and studies looking at if certain diets or macronutrient ratios are more effective for certain health conditions. For example, Virta Health utilizes a ketogenic diet for those suffering from Type 2 Diabetes and they have experienced great success in reversing Type 2 Diabetes. This is not to say a ketogenic diet is the only way to reverse Type 2 Diabetes though.
Remember, what has worked for others is not the only way. You may have other options, so I encourage you to work with someone who can provide you with more than one option to reach your health goals.
With that said, you will notice in the various Macronutrient Ratio Pie Charts that protein is kept constant. This is not to say that everyone should be getting 25% of calories from protein, but more so to highlight consuming adequate protein is incredibly important. I wrote a Three-Part Series on the nutrient protein you can check out here: Part 1, Part 2, Part 3.
Here are some examples of foods rich in Monounsaturated, Polyunsaturated and Saturated Fats.
Now comes the question of how can we use some of these foods; specifically, which oils or fats should we cook with?
I go back to the chemical structure of these fats. The most stable fats, if you recall, are saturated fats. Next, are monounsaturated fats and last, polyunsaturated fats. So when thinking of which fats to cook with I would go in that order, while avoiding or limiting your use of oils high in polyunsaturated fats. Cooking with obviously exposing these oils to heat, and heat increases the oxidation of these fats and creates lipid peroxides. Lipid peroxides wreak havoc within our bodies and require our antioxidant system to work to neutralize those peroxides. While a small amount of those foods is nothing to worry about and if you are using and eating primarily whole, minimally-processed ingredients you will naturally have a low intake of those oils. However, our modern food system contains many of these oils, whether you are eating out or eating packaged food item, you are most likely consuming these oils in larger amounts than what is best for your body.
Notice I specifically mention the oil, rather than the whole food, in the case of sunflower, sesame, flax, and chia. There is nothing wrong with consuming nuts and seeds that are higher in polyunsaturated fats. The whole food, in its raw form, contains antioxidants like Vitamin E which protect the polyunsaturated fatty acids from oxidizing. The oil form, depending on how it is processed, may already be oxidized by the time you use it; or if you plan on cooking with the oil, know the cooking process damages the oil. When using one of those oils, a cold- and/or expeller-pressed version is better, but ideally used for a dish that is not heated, e.g. a salad dressing.
A few final notes about these food sources. Fat is very calorically dense; more so than carbohydrates and protein. A few nuts or a tablespoon of olive oil is over 100 Calories, so keep this in mind when using and eating these foods. I like to use my thumb when trying to determine an appropriate portion size.
At this point I am hoping you have learned about the different types of fats; and, except for trans fats, created via partial hydrogenation, SFAs, MUFAs, and PUFAs are not bad. Granted the health implication of SFAs is murkier than that of MUFAs and PUFAs, but in the context of a diet consisting of whole, minimally-processed foods that include foods containing SFAs in conjunction with a healthy blood lipid profile, there shouldn’t be a concern.
How much fat you eat depends on your personal preference. There are numerous macronutrient ratios one can choose from, but what can you sustain long-term that allows you to meet your body composition and health goals? Remember, when it comes to weight loss, you need to be in a caloric deficit, regardless if you are eating high fat/low carb or low fat/high carb.
Fat is essential. Not only does our body require essential fatty acids, but consuming fat with plant foods allows us to absorb the fat-soluble vitamins in those foods. Don’t be afraid of fat, but be mindful of your intake. When cooking with fat using fats or oils rich saturated or monounsaturated fats is more ideal, from a stability standpoint. If you are trying to limit your intake of saturated fat due to concerns about blood lipid markers, opting for an avocado or olive oil is a great alternative.
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