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Fat in the diet is a never ending topic. For a long time, a high-fat diet was considered unhealthy.
Meanwhile unsaturated fatty acids, among them in particular Omega-3 fatty acids, considered healthy. Only saturated fat still has a questionable reputation.
But is this justified? In this article, we’ll explain the differences and provide you with a list of healthy sources of fat.
The function of fats in the human body
Let’s first get to the heart of what fat actually is and how it works in the body.
Fat has two essential functions in the human body.
1. Fat as an energy source
Fat, along with carbohydrates and proteins, is one of the three macronutrients from which we can obtain energy. However, compared to proteins and carbohydrates, it provides twice as much energy per gram.
So a high-fat diet is anything but low-calorie, and for this very reason many weight-conscious people try to avoid fat.
2. Essential fatty acids that perform biological functions
Fats serve not only as a source of energy, but also have important biological functions. For example, they are needed for cell membranes. Some fatty acids are essential.
Since we can’t make them ourselves, we have to take them from the food we eat. This is the polyunsaturated omega-3 fatty acid docosahexaenoic acid (DHA) and the omega-6 fatty acid arachidonic acid (AA).
Sources and function of omega-3 fatty acids
Officially, the vegetable fatty acids alpha-linolenic acid (ALA) and linoleic acid (LA) are considered essential. They can be broken down respectively into the fatty acids EPA and DHA, resp. are converted into AA. However, DHA and AA are the actual fatty acids needed by the body.
However, since the conversion rate is extremely inefficient (5-10%), it is difficult to meet omega-3 requirements with plant foods. 1 n-3 fatty acids in Indian diets – Comparison of the effects of precursor (alpha-linolenic acid) Vs product (long chain n-3 poly unsaturated fatty acids)
Omega-3 in particular is critical, as many people do not consume enough of it. To get enough omega-3, you should rely on animal sources, especially oily fish.
Meat is also a good source of omega-3, but be sure to eat pasture-raised meat, which has seven times more omega-3 fatty acids than meat from conventionally raised animals. 2 The essentials of essential fatty acids.
Function of Omega-6 Fatty Acids
Omega-6 fatty acids are also essential, but you don’t need to worry about them, because most people take too much of them. Besides the absolute amount, the ratio of omega-3 to omega-6 fatty acids is also important.
Omega-3 and omega-6 fatty acids are converted in the body by the same enzymes. 3 Dietary omega-3 and omega-6 fatty acids compete in producing tissue compositions and tissue responses. While omega-3 conversion products have a positive impact on health because they are vasodilators and anti-inflammatory, but those from omega-6 promote inflammation. 4 Omega-6 fatty acids and inflammation. 5 Omega-3 polyunsaturated fatty acids and inflammatory processes: nutrition or pharmacology?
The ideal omega-3 to omega-6 ratio is 1:1, but in fact the average ratio in Western cultures is 1:30! 6 Omega-6/Omega-3 Essential Fatty Acid Ratio: The Scientific Evidence
This is mainly due to the high consumption of bad vegetable oils, such as sunflower oil, which is a real omega-6 bomb. For a favorable omega-3 to omega-6 ratio you should avoid these oils at all costs.
Which foods are rich in unsaturated and saturated fatty acids??
Before we go into more detail about which fats are healthy and which are not, let’s take a look at which fats are found in which foods. After all, we eat fats in the form of foods, which always contain a mixture of fatty acids.
And here’s exactly the point we’re trying to make: vegetable fats are often equated with unsaturated fats, and animal fats with saturated fats. Nothing could be further from reality.
1. Animal fat sources for your body
Let’s take another animal fat with the worst reputation imaginable: pork lard. Just thinking about it, many people have pictures in their minds of how this fat literally gums up the arteries.
Anyone who says that saturated fat is unhealthy and that you should eat fish rather than meat is contradicting themselves.
Healthy animal fat sources:
- Meat from pasture raised
- Eggs from free range
- Wild caught fish
- Butter from pasture-raised animals
- Lard from pasture-raised pigs
- Fish oil
- Cod liver oil
2. Plant fat for your body
How does it look the other way around with vegetable fats – does vegetable equal unsaturated?
Vegetable equals unsaturated in most cases, but even here there are clear exceptions.
Good plant sources of fat:
- Avocados/avocado oil
- Coconut oil
- Olive oil
- Nuts (No more than a handful per day)
- Cocoa butter
Conclusion: Animal and vegetable fat sources
The fat composition of food is much more complex than it is generally portrayed. This already shows that the statement that animal fats are unhealthy because they are saturated stands on very shaky ground.
How much and which fat is healthy?
It is becoming more and more apparent that the specific proportion of fat, protein and carbohydrates plays a subordinate role in health. It is much more important to eat natural foods.
The ketogenic diet is an extreme example, as the fat content is particularly high here. Even here, however, there is no evidence that the high fat is in any way harmful.
Thus, a ketogenic diet leads to an improvement in blood levels within a short period of time. Total cholesterol may increase, but it is now known that this value is not meaningful.
What about cholesterol?
However, keto also increases LDL, which is known as "bad" cholesterol. 17 Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. However, the division into HDL as "good" cholesterol and LDL as "bad" cholesterol is highly simplified and not correct.
LDL consists of several subfractions. There’s once small, dense LDL that increases the risk of heart disease, but that doesn’t apply to larger LDL particles. 18 Role of plasma triglyceride in the regulation of plasma low density lipoprotein (LDL) subfractions: relative contribution of small, dense LDL to coronary heart disease risk.
However, consumption of saturated fat shifts the ratio toward the larger LDL particles. 19 Change in dietary saturated fat intake is correlated with change in mass of large low-density-lipoprotein particles in men. Unfortunately, the various subfractions of LDL are not measured in a standard blood test, and then the alarm is often wrongly raised in people on a keto diet.
A high consumption of unsaturated fatty acids, on the other hand, does not cause LDL to rise. 20 Effect of dietary fatty acids on serum lipids and lipoproteins. A meta-analysis of 27 trials. However, it is debatable whether replacing saturated fat with unsaturated fat is beneficial from a health perspective.
Like total cholesterol, LDL levels do not seem to be very meaningful, as it is the quality of LDL that is more important.
Important blood values that are strongly related to fat
So how can you tell if your blood values are okay?? Two values and their relationship to each other are particularly important.
These are the triglycerides, the so-called blood lipid value. This value should be as low as possible, preferably below 150 mg/dl. 22 Triglycerides: Why do they matter?? Interestingly, triglyceride levels decrease with a high-fat, low-carbohydrate diet.
How can this be?
In a low-carbohydrate diet, the body uses fat as an energy source. So the fat, instead of floating around unused in the blood, is taken up by the cells and burned off.
However, a carbohydrate and sugar-heavy diet cannot burn fat efficiently. This is particularly noticeable in the case of progressive insulin resistance, and as a result the level of triglycerides in the blood increases.
2. HDL cholesterol
The second important value is HDL, which is known as "good" cholesterol. This value should be as high as possible, preferably above 60 mg/dl. 23 HDL cholesterol: How to boost your ‘good’ cholesterol The ratio between triglycerides and HDL (TG/HDL) should ideally be below 2. 24 The Triglyceride/HDL Cholesterol Ratio
So does it make a difference whether the fats are saturated or unsaturated?? As long as fat is considered an energy source, it does not play a major role. Saturated fats have the great advantage of being incredibly stable.
Even at high temperatures not much happens and they are available to the body as a clean energy source. However, unsaturated fat, especially polyunsaturated fat, is very unstable and oxidizes easily.
This causes them to react with molecules they should not interact with, such as proteins and DNA, thus triggering oxidative stress.
Fat in the ketogenic diet
In the ketogenic diet, fat is the main source of energy. A ketogenic diet puts the body in a state of ketosis, where ketone bodies are made from fat for energy.
In principle, any diet that gets you into ketosis is ketogenic. The most important thing here is to keep the carbohydrate content as low as possible.
The protein and fat content is variable, but classically the carbohydrates are replaced by fat and the protein content is kept moderate. So with keto, easily 70 -80% of energy is derived from fat.
What exactly the fatty acid composition looks like in keto is highly variable. However, as you can probably guess by now, a ketogenic diet is by no means all saturated fat.
The main sources of saturated fat are in keto:
- Coconut oil
- Butter from pasture
Unsaturated fat in keto:
- Fish from wild catch
- Meat from pasture-raised free-range animals
- Olive oil
So the fatty acid composition depends on how much and in what proportion you eat these foods.
Since you are eating a lot of fat on keto, it is especially important to make sure you are eating healthy fats. The proportion of saturated and unsaturated fatty acids is of secondary importance. All natural fats are healthy.
What do we mean by natural fats?
These are all fats that occur naturally in foods or can be easily extracted from them. So you don’t have to worry about fat in fish, meat, and eggs – one less thing to worry about.
For the fats and oils you use for frying, cooking, or salad dressing, you need to know roughly how they were obtained. Olive oil, butter, lard and coconut oil can be easily extracted from the respective foodstuff without complex procedures.
You could also make this yourself if necessary. You probably don’t want to do this and it’s not necessary – it’s just a matter of principle.
However, sunflower oil, rapeseed oil and margarine are highly processed finished products that you should avoid at all costs.
Their production requires industrial processes with a lot of pressure and high temperatures, during which especially the unstable polyunsaturated fatty acids (which make up the main part of these oils) oxidize easily and thus become a source of danger for health.
The source of the fats is crucial
So, in summary, the exact ratio of unsaturated to saturated fatty acids is beside the point. Also how much fat you eat is not important.
If you are on a ketogenic diet, the fat content is very high. However, while the ketogenic diet offers many health benefits, it is not the holy grail.
A diet with less fat and more carbohydrates can also be healthy, as long as you do not replace the fat with highly processed carbohydrates and sugar.
Instead, you should make sure to eat only natural fats and also enough omega-3 fats.