Are Fats Bad?

We are going to explain why fats are not bad for your health for the most part and which ones you have to avoid to reduce the risk of developing complex diseases.
Are Fats Bad?
Saúl Sánchez

Written and verified by el nutricionista Saúl Sánchez.

Last update: 07 July, 2023

For many years it was claimed that fats are bad for your health. However, today experts have a very different opinion of these nutrients. Although it’s true that there are lipids of different qualities, as a general rule they are beneficial elements.

It must be taken into account that the origin of the fats is an important factor, as well as the physicochemical treatments that they have undergone. There are several groups of lipids and not all of them fulfill the same functions, although most of them are necessary for the proper functioning of the human body.

Types of fats that exist

The first thing that needs to be made clear are the different types of fats that exist. These nutrients are made up of units called fatty acids, and can be classified according to two criteria.

The first one has to do with the presence of double bonds in its chemical structure. The second focuses on the spatial arrangement of molecules in space.

Saturated fats

Are fats bad? In their fair measure, these are not harmful
Although foods of animal origin, such as red meat, are frequently associated with protein, they actually contain large amounts of fat.

Taking into account the presence (or lack) of double bonds in its interior, we can establish the set of saturated fats. These are mostly of animal origin, and don’t contain double bonds joining the elements that make them up. This doesn’t mean that there are no saturated lipids of plant origin – it’s also possible to find them.

Throughout the 20th century, it was proposed that the regular intake of saturated fatty acids could cause an increase in cardiovascular risk. It was established that there was a relationship between the consumption of these nutrients and the increase in serum cholesterol. It has now been shown that this is not the case. This is stated in a study published in the journal Critical Reviews in Food Science and Nutriton.

It isn’t possible to find solid evidence that associates regular intake of unsaturated lipids with a greater number of cardiovascular events. Nor can it be said that these nutrients are capable of increasing the incidence of cancer, since a strong causal relationship has not been confirmed either.

For this reason, the recommendation regarding the consumption of saturated fats has been greatly liberalized. Although the presence of these nutrients in the diet was limited for several years, today a much higher contribution is allowed. However, this doesn’t mean that they represent a higher percentage in the diet than the rest of the lipids that we’ll see below.

Monounsaturated fats

Monounsaturated fats contain a double bond in their chemical structure. This gives them physicochemical properties different from those of the saturated type. The latter are solid at room temperature, while the unsaturated are usually liquid and less sensitive to changes in temperature.

From the 1970s on, monounsaturated fats began to be considered beneficial for health. They are found mainly in foods of plant origin, such as nuts, oils, and seeds. Also, some animals can be a source of these nutrients, as is the case of pigs fed with acorns or cows that eat grass.

As a general rule, these elements are considered beneficial for health, since they have an anti-inflammatory potential. According to research published in The Journal of Nutrition, these nutrients are capable of protecting against cardiovascular pathologies when they are introduced into a varied and balanced diet.

In fact, it is proposed that its regular consumption improves the lipid profile, increasing HDL and reducing LDL. However, there is currently considerable controversy about the actual influence of cholesterol on the risk of heart-related problems. It is a subject of debate among experts with physiological aspects that are not yet well explained.

Polyunsaturated fats

For their part, polyunsaturated fats are those that have several double bonds in their chemical structure. Despite having a liquid texture at room temperature, they are the ones that best withstand changes from the physicochemical point of view. They resist heat well and have a higher smoke point than saturated or monounsaturated ones.

Typically, these types of lipids are found in oily fish, grass-fed meats, and some plant-based products, such as extra virgin olive oil. Among all the fatty acids that make up these nutrients, special mention must be made of those of the omega 3 series and those of the omega 6 series.

The former are able to generate a powerful anti-inflammatory effect in the body, as stated by research published in the journal International Immunology . They can be used to prevent cardiovascular problems or to treat other pathologies such as arthritis, inflammatory bowel diseases, some chronic pain, among other conditions.

For their part, the lipids of the omega-6 series have an inflammatory potential. This doesn’t mean that they are harmful to the body. Rather, the complete opposite. Inflammation is a natural process essential for life. It is simply key to maintain an adequate omega 3-omega 6 ratio to prevent the inflammatory mechanism from being overly favored, which could be counterproductive.

Experts and nutritional guides affirm that the optimal ratio between both types of fatty acids is 1:2 or 1:3 in favor of omega 6. However, most people’s diets show values that are far from this ideal, reaching proportions greater than 1:10. This situation could produce a state of low-grade chronic inflammation that is detrimental in the medium term.

To correct this imbalance, you simply need to carry out an optimal dietary intervention. Promoting the consumption of fresh foods over processed ones is an appropriate strategy to regain a healthy fatty acid balance. In the same way, it’s best to increase the presence of fish in the diet.

Cis and trans fatty acids

We have talked about fatty acids according to their chemical structure and the presence of double bonds inside. Now, there is another classification that allows lipids to be included in two groups according to their spatial arrangement, something that determines their health in a much finer way.

As a general rule, any fatty acid found in fresh food, whatever it may be, will be of the cis type. At the moment in which the said product is subjected to a significant physicochemical alteration, such as an aggressive thermal process, it can be transformed into a trans type. This class of lipids is considered bad for health.

According to a study published in the journal Diabetes & Metabolic Syndrome, these elements are capable of increasing the incidence of complex pathologies such as diabetes, cancer, or cardiovascular diseases. They promote inflammation and oxidation in the body, generating alterations in normal and daily physiological processes.

For this reason, it’s essential to limit the presence of these fatty acids in the diet. To do this, we must reduce the consumption of ultra-processed foods and apply mild cooking methods to fresh products. Examples of the latter are the grill, the oven, steaming or boiling.

However, it must be borne in mind that not all fatty acids have the same facility to transform to the trans type. The saturated ones, due to the absence of double bonds inside, are more sensitive to high temperatures, so their molecules move in space more easily. You have to be more careful when cooking this kind of product.

However, fatty acids of the unsaturated type are better at resisting temperature increases, so they have less danger in this regard. This doesn’t mean that you can fry food in olive oil with complete peace of mind, but it does mean that less trans-type acids are generated than if the frying is done with butter.

How much fat can be introduced into the diet?

Are fats bad? As long as you don't eat trans fats, there aren't too many problems
The amount of fat to include in the diet depends on what you are looking for from a nutritional point of view. However, it is important to cook in such a way as to avoid trans fats.

Now you know that fats are not necessarily bad. But all the nutrients have to be consumed in their proper measure. For this reason, it’s important to know in what proportion they must appear in the diet. In this way you can take advantage of its benefits and functions.

As a general rule, it’s recommended that at least 25-30% of total calories come from lipids. This amount could be higher in the case of ketogenic diets, since these are characterized by limiting carbohydrates.

In the case of a healthy sedentary adult, the optimum would be to guarantee between 40 and 70 grams of fat per day. Of course, it’s important for their profile to be adequate. The saturated ones could account for 10% of the total, the unsaturated are those that have a greater role.

As we have commented, one of the objectives is to balance the omega 3-omega 6 ratio. With this strategy, it is possible to improve a person’s state of health in the medium term, as stated in a study published in the journal Prostaglandins, Leukotrienes and Essential Fatty Acids. To do this, avoid ultra-processed foods and prioritize fish intake over meat.

What foods with fats to include in the diet?

To ensure the presence of quality fats in the diet, it is important to ensure the consumption of fresh food. Oily fish and organic meats are always an excellent option, since they also provide proteins of high biological value. Eggs contain saturated lipids, as well as dairy. However, they are cis fatty acids, that is to say, of good quality.

When cooking, it is important to avoid butter and margarine. This type of product is poorly resistant to the increase in temperature, which is why the lipids they contain are transformed into a trans type. To reduce the risk, it is always advisable to use high-quality vegetable oils. Both extra virgin olive oil and avocado oil could be a good option.

On the other hand, the fat intake can be completed by means of oily fruits such as avocado, through nuts and with the inclusion of seeds in the diet. Within this last group, those made of flax, chia, and sesame stand out. However, with all these products you have to be careful, since they are high in calories.

An excess of fat in the diet, although good, could lead to an increase in body weight. The energy balance is thrown out of balance in favor of intake, causing problems. This change in body composition would be harmful in the medium term. For this reason, consuming too many lipids can be counterproductive.

What about fat supplements?

In recent years, the consumption of fat supplements has become popular, especially acids from the omega 3 series, to improve some aspects related to health. According to a study published in The Journal of Nutritional Biochemistry, these nutrients could help fight obesity and metabolic syndrome. To do this, they have to be consumed in the context of a healthy diet.

The truth is that in the world of sports the inclusion of fatty acid supplements is quite common. Their anti-inflammatory nature is used above all to generate a better recovery. This reduces ailments and the feeling of heaviness at the muscular level.

These products can also be consumed to improve rheumatoid processes such as arthritis. However, it is always a good idea to consult with a nutritionist before beginning to take supplements. It is important that they guide the dosage and evaluate the need to supplement with fatty acids.

Fats are not bad for your health

As discussed, fats are not bad for your health. In fact, almost all of them are good, although in moderation. It’s true that it’s essential to reduce the contribution of trans fatty acids. However, it isn’t necessary to completely avoid their intake, as even breast milk contains them.

The key is to find a balanced situation. This need is exemplified by the omega 3-omega 6 ratio. When the consumption of both elements is more or less even, a situation of homeostasis is reached in the internal environment. Thanks to this, inflammatory processes are controlled, which reduces the incidence of many complex pathologies.

  • Szajewska, H., & Szajewski, T. (2016). Saturated Fat Controversy: Importance of Systematic Reviews and Meta-analyses. Critical reviews in food science and nutrition56(12), 1947–1951.
  • Tindall, A. M., McLimans, C. J., Petersen, K. S., Kris-Etherton, P. M., & Lamendella, R. (2020). Walnuts and Vegetable Oils Containing Oleic Acid Differentially Affect the Gut Microbiota and Associations with Cardiovascular Risk Factors: Follow-up of a Randomized, Controlled, Feeding Trial in Adults at Risk for Cardiovascular Disease. The Journal of nutrition150(4), 806–817.
  • Ishihara, T., Yoshida, M., & Arita, M. (2019). Omega-3 fatty acid-derived mediators that control inflammation and tissue homeostasis. International immunology31(9), 559–567.
  • Islam, M. A., Amin, M. N., Siddiqui, S. A., Hossain, M. P., Sultana, F., & Kabir, M. R. (2019). Trans fatty acids and lipid profile: A serious risk factor to cardiovascular disease, cancer and diabetes. Diabetes & metabolic syndrome13(2), 1643–1647.
  • Harris W. S. (2018). The Omega-6:Omega-3 ratio: A critical appraisal and possible successor. Prostaglandins, leukotrienes, and essential fatty acids132, 34–40.
  • Albracht-Schulte, K., Kalupahana, N. S., Ramalingam, L., Wang, S., Rahman, S. M., Robert-McComb, J., & Moustaid-Moussa, N. (2018). Omega-3 fatty acids in obesity and metabolic syndrome: a mechanistic update. The Journal of nutritional biochemistry58, 1–16.

Este texto se ofrece únicamente con propósitos informativos y no reemplaza la consulta con un profesional. Ante dudas, consulta a tu especialista.