There is still a widespread belief that dietary fats are something dangerous to health and that their consumption causes increased body fat and overweight.
Actually, fats are essential macronutrients for our body and should account for at least 28-30% of daily calories introduced with the diet. Fats are not only the main source of energy reserve of our body but are also the main constituents of all biological membranes, are vital for the absorption of essential vitamins, and perform an important endocrine function, being precursors of hormones.
People who follow a strongly low-fat diet, thinking that it is healthy, therefore make a significant mistake, especially if it replaces fats with an excess of sugars or animal proteins.
When talking about fats, we should not demonize them all, however, it is important to make a distinction between healthy fats and unhealthy fats, which, instead, should be strictly limited in daily nutrition. There are some types of dietary fats, in fact, that are responsible for the increase in "bad" cholesterol (LDL), waist circumference, and body inflammation, providing for chronic degenerative and especially cardiovascular diseases.
Unfortunately, there is still a lot of confusion about the intake and quality of fats in the diet: that is why we have decided to clarify and explain once and for all what are the differences between healthy and unhealthy fats, what effects they have on our health and in what foods we can find them.
How to classify fats
Defining dietary fats as good fats and bad is an easy way to indicate their ability to have positive or negative effects on our health.
From a chemical point of view, fats can be classified on the basis of their structures that can vary considerably by both hydrocarbon chain length and saturation status. Although hydrocarbon chain length is an important determinant of function, fats are often classified based on whether or not the fatty acid carbon chain contains no double bonds (Saturated Fatty Acids SFA), one double bond (Mono Unsaturated Fatty Acids, MUFA), or more than one double bond (Poly Unsaturated Fatty Acids, PUFA), as well as the configuration of the double bonds.
In addition, PUFAs are often further classified based on the position of the first double bond, creating n-3 and n-6 fatty acids. It is the differences in chain length and saturation status that dictate their performance in food and cooking, as well as their role in the body and impact on human health and disease risk.
Food fats can be also distinguished into liquid and solid fats (at room temperature). Solid fats are rich in SFA and are mainly animal-derived fats that we find in milk derivatives, meat, or eggs. Liquid dietary fats are rich in MUFA and are mainly plant-derived: we find them in vegetable oils such as olive oil, but also in dried fruits and oilseeds. PUFA are those of marine derivation, which we find in fish oil, krill oil, and algae, but we can also find them in some oily seeds such as nuts or flax seeds.
There is also a category of fats, hydrogenated fats, which undergo industrial processing processes, to switch from a liquid form to a solid form. We find these fats in packaged products and for example in vegetable margarine.
What are healthy fats?
Several studies have shown that there are good fats that protect our health and have a preventive effect on some chronic degenerative diseases.
The structure of each fatty acid differs, so it is reasonable that individual fatty acids might have unique impacts on health. The impact of specific fatty acids on disease incidence is difficult to elucidate, as the chronic disease develops over many years and is the culmination of many genetic and lifestyle factors.
This complexity makes randomized controlled trials of dietary interventions largely impractical, but these trials, coupled with observational, epidemiologic, and mechanistic studies, provide valuable evidence on the health effects of dietary fat and specific fatty acids.
Many studies show that some types of MUFA, such as oleic acid, contained in large quantities in extra virgin olive oil are healthy fats with beneficial and preventive properties against several chronic diseases. Oleic acid is undoubtedly the most important and well-known monounsaturated fatty acid, capable of conferring peculiarities interested in foods that are rich in it. The high stability, which results in high resistance to heat and oxidation, improves the shelf life of these foods and makes them suitable for cooking as well.
A diet rich in oleic acid favors the maintenance of normal blood fluidity and reduces LDL cholesterol (bad cholesterol), while it has no important effect on the level of triglycerides and HDL cholesterol (good cholesterol).
Monounsaturated fats should be most represented in the diet.
Foods rich in polyunsaturated fats can also have positive implications on human health, but unlike monounsaturated foods they are less stable, oxidize more easily and for this reason, they do not store for long and should not be heated.
What are unhealthy fats?
Many epidemiological and observational studies have shown the negative effects of the "Western Diet" on health and in particular on the possibility of being predisposed to diseases such as diabetes, or cardiovascular problems.
The "Western Diet" is rich in animal-derived saturated fats, but also refined sugars and industrial products, rich in hydrogenated fats. The latter, in particular, are those potentially most harmful to health and linked to the increase in bad cholesterol (LDL), decrease in HDL protective cholesterol and increase in body inflammation.
The importance of dietary pattern
Now you know the differences between healthy and unhealthy fats you may think that a diet rich in good fats is the best one to stay healthy and prevent chronic degenerative diseases.
Attention, this is not exactly the case!
Remember that it is important to take an adequate amount of good fats, without exceeding, and limit the unhealthy fats, but it is also essential to follow a healthy diet with a correct balance of macro and micronutrients (carbohydrates, proteins and fats, vitamins and minerals) and keep you active, combining healthy foods and physical activity, which means having a correct lifestyle.
This is the only key to raising our healthy life expectancies and living happily!
Author: Francesca Deriu, Nutritionist at Minutro
Ann G. Liu, A healthy approach to dietary fats: understanding the science and taking action to reduce consumer confusion Nutrition Journal (2017) 16:53
Position of the Academy of Nutrition and Dietetics: Dietary Fatty Acids for Healthy Adults
Heather Seid and Michael Rosenbaum Low Carbohydrate and Low-Fat Diets: WhatWe Don’t Know and Why We Should Know It Nutrients 2019, 11, 2749