Fats: good or bad for your health?

Fats have long been considered the enemy of our diet. Between misconceptions and alarming messages, many people believe that they should be avoided at all costs in order to stay healthy or lose weight. But the reality is more nuanced. Not all fats are created equal: some are essential for the body to function properly, while others, when consumed in excess, can have negative effects.

In this article, we will take a simple look at the different types of fats, their role in the body, and how to make the right choices for your everyday health.

 

What are fats?

Fats, also known as lipids, are nutrients that are essential for our bodies to function properly. For years, they were demonised, but today we know that not all fats are the same and that they should not be avoided, even when trying to manage your weight. Our needs are estimated at 35-40% of our energy intake.

 

The role of fats

Fats have essential functions within our bodies:

  • - they are the main components of our cells: they are therefore one of the basic elements of our body and brain
  • - they are a very important source of energy and represent the largest form of storage in our body (in the form of triglycerides in adipocytes)
  • - they enable the transport of essential vitamins: vitamins A, D, E and K
  • - they help to regulate inflammation, particularly in certain inflammatory conditions (such as polyarthritis and spondylitis)
  • - they are essential for the synthesis of hormones (oestrogen, progesterone and testosterone, the main precursor of which is cholesterol)

 

Different types of fat

When you eat foods rich in fat, such as butter and oil, you are eating a mixture of triglycerides made up of fatty acids. Depending on the foods you eat, there are several types of fatty acids, each with different effects on health.

 

Saturated fatty acids

Their main role is to provide energy. When found naturally in food, they can have positive effects on health.

However, when consumed in excess, especially with a diet high in sugar, they can increase the risk of cardiovascular disease, upset the balance of gut flora and promote inflammation in the body. They should therefore be consumed in moderation [1, 2].

Where are they found? In cheese, butter, fatty meats, processed meats, palm oil, coconut oil and certain high-fat processed foods.

 

Trans fatty acids

Trans fatty acids are naturally present in small amounts in certain foods, particularly in dairy fats (butter, cheese, cream, etc.), in the form of trans-vaccenic acid. They are also found in many industrial products containing vegetable fats that have been modified to achieve a particular texture. For example, the crispness of puff pastry or the creaminess of a spread are often achieved through a process called partial hydrogenation, which alters the structure of vegetable oils.

However, when they come from industrial sources, these trans fatty acids are associated with an increased risk of cardiovascular disease and insulin resistance [2-4].

Where are they found? Unfortunately, they are widely present in a wide variety of processed products, with no obligation to mention their presence on packaging. They can be found in pastries, bread, cakes, biscuits, products made with puff pastry, shortcrust pastry or shortbread, margarine, crisps and savoury snacks.

Be vigilant: if you buy this type of food, pay attention to the words “partially hydrogenated vegetable oil” in the list of ingredients.

 

Monounsaturated fatty acids

Among these, oleic acid is the most abundant plant-based omega-9 in the diet. It is the main component of olive oil, which is recognised as promoting cardiovascular protection and regulating inflammation when included in a healthy diet. It contributes to good cardiovascular health. Monounsaturated fatty acids are also known to help prevent type 2 diabetes and metabolic syndrome, so they should be encouraged. [5, 6]

Where can it be found? Olive oil, hazelnuts and avocados are particularly rich sources.

 

Polyunsaturated fatty acids

There are two types of polyunsaturated fatty acids: omega-6 and omega-3.

Omega-6

Arachidonic acid is a type of fat in the omega-6 family, found mainly in animal products such as red meat (beef, pork), processed meats, butter, cheese and cream. If consumed in excess, it can promote inflammation in the body and increase the risk of cardiovascular problems. Unfortunately, it is often found in excess in the modern Western diet. [7]

Plant-based omega-6 fatty acids, such as linoleic acid, are mainly found in certain oils (sunflower, grape seed, corn). These oils are widely used and should also be consumed in moderation. However, some vegetable oils, such as evening primrose oil and borage oil, can have positive effects, particularly on hormonal balance and skin quality.

Omega-3 fatty acids

Omega-3 fatty acids are very important for good health. They help cells function properly and play a positive role in reducing inflammation in the body. Unfortunately, most people do not consume enough, especially in Western countries. [7-9]

There are several types of omega-3:

  • - ALA (alpha-linolenic acid) comes from plants. It is found in foods such as rapeseed oil, linseed oil, hemp oil, walnuts, linseeds and chia seeds.
  • - EPA and DHA come mainly from oily fish (salmon, mackerel, sardines, anchovies, etc.) and certain algae.
  •  

EPA helps to calm inflammation, while DHA is essential for the brain and body's cells. Both play an important role in preventing certain diseases and maintaining good health. [10,11]

A balance between omega-6 and omega-3 intake is key to good health. The ratio should be 1g of omega-3 to 3g of omega-6, but the current British diet provides an average of 1g of omega-3 for more than 12g of omega-6. [12, 13]

 

In practice

Optimise your omega-3 intake

  • - Every day, consume at least 2 tablespoons of rapeseed, walnut or camelina oil (organic, virgin, first cold-pressed) as a dressing on a portion of raw vegetables, cooked vegetables or starchy foods.
  • - Eat small oily fish such as sardines, mackerel or anchovies once or twice a week. Due to their mercury content, salmon and trout should be limited.
  • - Eat a handful of walnuts per day (30g).
  • - Choose products from the ‘blue-white-heart’ label scheme, as these are richer in DHA.
  • - Supplement your intake with chia seeds. These can be added to plant-based yoghurt, salads or desserts to give them texture.

 

Choose foods rich in oleic acid

  • - At least 1 to 2 tablespoons of organic, extra virgin or virgin olive oil. Olive oil is relatively good for cooking (never exceed the smoke point).
  • - Half an avocado twice a week: to limit the dramatic environmental consequences of overproduction.
  • - 1 handful of hazelnuts and almonds per day

 

On the other hand, limit the following foods

  • - Fatty meats: maximum once a week, especially from intensive farming. Choose meat from pasture-raised or animal-friendly farms.
  • - Dairy fats (butter, cream, cheese).
  • - Processed foods high in fat: all foods that list ‘partially hydrogenated’ oil or fat in the ingredients, such as puff pastry and margarine, should be avoided.

 

Conclusion

So, to the question of whether fats are good or bad for your health, the answer is ‘it all depends on the type of fat consumed and in what quantity’.

As we have seen above, our bodies need fats to perform vital functions such as hormone production, brain health and the absorption of certain vitamins. The important thing is to choose the right sources.

 

 

Sources :

[1] Blekkenhorst, Lauren C., et al. “Dietary Saturated Fat Intake and Atherosclerotic Vascular Disease Mortality in Elderly Women: A Prospective Cohort Study2.” The American Journal of Clinical Nutrition, vol. 101, no. 6, June 2015, pp. 1263–68, https://doi.org/10.3945/ajcn.114.102392.

[2] Souza, Russell J. de, et al. “Intake of Saturated and Trans Unsaturated Fatty Acids and Risk of All Cause Mortality, Cardiovascular Disease, and Type 2 Diabetes: Systematic Review and Meta-Analysis of Observational Studies.” BMJ, vol. 351, Aug. 2015, p. h3978, https://doi.org/10.1136/bmj.h3978.

[3] Mozaffarian, D., et al. “Health Effects of Trans-Fatty Acids: Experimental and Observational Evidence.” European Journal of Clinical Nutrition, vol. 63, no. 2, May 2009, pp. S5–21, https://doi.org/10.1038/sj.ejcn.1602973.

[4] Hu, Frank B., et al. “Dietary Fat Intake and the Risk of Coronary Heart Disease in Women.” New England Journal of Medicine, vol. 337, no. 21, Nov. 1997, pp. 1491–99, https://doi.org/10.1056/NEJM199711203372102.

[5] Schwingshackl, L., et al. “Effects of Monounsaturated Fatty Acids on Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis.” Annals of Nutrition and Metabolism, vol. 59, no. 2–4, Dec. 2011, pp. 176–86, https://doi.org/10.1159/000334071.

[6] Schwingshackl, Lukas, and Georg Hoffmann. “Monounsaturated Fatty Acids, Olive Oil and Health Status: A Systematic Review and Meta-Analysis of Cohort Studies.” Lipids in Health and Disease, vol. 13, no. 1, Oct. 2014, p. 154, https://doi.org/10.1186/1476-511X-13-154.

[7] ANSES: “Apports en acides gras de la population vivant en France et comparaison aux apports nutritionnels conseillés définis en 2010”. Consulté le 01/07/2025. Disponible sur https://www.anses.fr/fr/system/files/NUT2014sa0117Ra.pdf

[8] Calder, Philip C. “Omega‐3 Polyunsaturated Fatty Acids and Inflammatory Processes: Nutrition or Pharmacology?” British Journal of Clinical Pharmacology, vol. 75, no. 3, Mar. 2013, pp. 645–62, https://doi.org/10.1111/j.1365-2125.2012.04374.x.

[9]Calder, Philip C. “Omega-3 Fatty Acids and Inflammatory Processes: From Molecules to Man.” Biochemical Society Transactions, vol. 45, no. 5, Sept. 2017, pp. 1105–15, https://doi.org/10.1042/BST20160474.

[10] Kew, Samantha, et al. “Effects of Oils Rich in Eicosapentaenoic and Docosahexaenoic Acids on Immune Cell Composition and Function in Healthy Humans123.” The American Journal of Clinical Nutrition, vol. 79, no. 4, Apr. 2004, pp. 674–81, https://doi.org/10.1093/ajcn/79.4.674.

[11] Lee, Tak H., et al. “Effect of Dietary Enrichment with Eicosapentaenoic and Docosahexaenoic Acids on in Vitro Neutrophil and Monocyte Leukotriene Generation and Neutrophil Function.” New England Journal of Medicine, vol. 312, no. 19, May 1985, pp. 1217–24, https://doi.org/10.1056/NEJM198505093121903.

[12] Simopoulos, A. P. “The Importance of the Ratio of Omega-6/Omega-3 Essential Fatty Acids.” Biomedicine & Pharmacotherapy, vol. 56, no. 8, Oct. 2002, pp. 365–79, https://doi.org/10.1016/S0753-3322(02)00253-6.

[13] Harris, William S. “The Omega-6:Omega-3 Ratio: A Critical Appraisal and Possible Successor.” Prostaglandins, Leukotrienes and Essential Fatty Acids, vol. 132, May 2018, pp. 34–40, https://doi.org/10.1016/j.plefa.2018.03.003.