Fats: which ones to favor, which ones to avoid?

What if I was wrong to be wary of all fats for years?

For several decades, fats have been designated as the main culprits of cardiovascular disease and weight gain. The all-fat low-fat fashion dominated the 1980s and 2000s, before scientific research profoundly nuanced this message. Today, the consensus is clear: not all fats are equal, far from it. Some are essential for my health, others should be limited, and some should really be avoided. Sorting things out is the purpose of this article.

1. Lipids: an essential macronutrient

Lipids, commonly known as fats, are one of the three essential macronutrients along with carbohydrates and proteins. Contrary to popular belief, removing them from my diet would be a serious mistake. They play fundamental biological roles:

• ●Constitution of cell membranes: phospholipids form the double lipid layer of all cells in the body

• ●Hormonal synthesis: steroid hormones (estrogens, testosterone, cortisol) are synthesized from cholesterol

• ●Transport of fat-soluble vitamins: vitamins A, D, E and K can only be absorbed in the presence of dietary fats

• ●Thermal insulation and protection of vital organs

• ●Dense energy source: 1 g of lipids provides 9 kcal, compared to 4 kcal for proteins and carbohydrates

• ●Functioning of the nervous system: the brain is made up of approximately 60% fat

ANSES recommendations place the optimal lipid intake between 35 and 40% of the total daily energy intake. The real issue is therefore not the total quantity of fats, but their quality and diversity.

Type fatty acid	Main sources	Health effects
Saturated fatty acids (AGS)	Red meat, cold meats, butter, cheese, coconut oil, palm oil	In excess: increases LDL cholesterol and cardiovascular risk. To be limited without eliminating.
Monounsaturated fatty acids (MUFA)	Olive oil, avocado, cashews, almonds, hazelnuts	Beneficial: lower LDL, maintain HDL. Pillar of the Mediterranean diet.
Omega-6 polyunsaturated fatty acids	Sunflower oil, corn oil, nuts, sunflower seeds	Essential but often in excess in Western diets. Omega-6/omega-3 ratio to balance.
Omega-3 polyunsaturated fatty acids	Fat fish, flaxseed oil, walnuts, chia seeds, rapeseed oil	Strongly beneficial: anti-inflammatory, cardiovascular and neuronal protection.
Trans fatty acids (AGT)	Hydrogenated margarines, industrial pastries, industrial fried foods	Avoid absolutely: increase LDL, decrease HDL, pro-inflammatory.

2. The classification of fatty acids: what I need to know

Dietary fats are composed of fatty acids, classified according to their chemical structure into three main categories:

3. Omega-3: the fats I lack the most

Omega-3 fatty acids are among the most deficient nutrients in contemporary Western diets. However, their role in the prevention of numerous pathologies is one of the best documented in nutrition.

There are three main types:

• ●ALA (alpha-linolenic acid): plant precursor, present in flax seeds, nuts, rapeseed oil. It must be provided through food because the body cannot synthesize it.

• ●EPA (eicosapentaenoic acid): marine form with direct anti-inflammatory action, present in fatty fish (salmon, mackerel, herring, sardines, anchovies).

• ●DHA (docosahexaenoic acid): marine form essential for the development and functioning of the brain and retina. Presented in the same sources as the EPA.

ANSES recommendations recommend 2 servings of fatty fish per week to cover EPA and DHA needs. In France, less than a third of the population achieves this objective according to consumer studies.The omega-6/omega-3 ratio is also crucial: the Western diet has an average ratio of 15:1 to 20:1, while the optimal ratio would be 4:1 to 1:1. This imbalance promotes a chronic low-grade inflammatory state, implicated in many chronic pathologies.

4. Trans fats: the only ones really to be banned

Among all fats, industrial trans fatty acids are the only ones whose total elimination is recommended by all health authorities. Produced during the partial hydrogenation of vegetable oils, they are doubly harmful:

• ●They increase LDL-cholesterol (bad cholesterol)

• ●They simultaneously reduce HDL-cholesterol (good cholesterol)

• ●They promote systemic inflammation and insulin resistance

• ●They are associated with an increased risk of coronary heart disease, stroke and type 2 diabetes

Good news: in Europe, regulations have strongly regulated their use since 2021, with a legal limit of 2 g of trans fatty acids per 100 g of fat in processed products. However, imported ultra-processed products and industrial fried foods may still contain them. I spotted them on the labels under the words partially hydrogenated oils or hydrogenated vegetable fats.

5. My concrete choices on a daily basis

Armed with this knowledge, here is how I optimize my fat intake in a simple and sustainable way:

• ●For cooking: I prefer extra virgin olive oil (resistant well to moderate heat) or coconut oil in small quantities for cooking at high temperatures. I avoided sunflower and corn oils when cooking.

• ●For seasoning: rapeseed oil is one of the best for salad dressings and cold seasonings, thanks to its excellent omega-6/omega-3 ratio. I alternate it with olive oil.

• ●For fatty proteins: I eat fatty fish (salmon, mackerel, sardines, herring) at least twice a week. I limit red meat to 500 g per week maximum.

• ●For snacks: a handful of oilseeds (walnuts, almonds, hazelnuts) rather than an industrial biscuit. Walnuts are particularly rich in ALA, a precursor to omega-3.

• ●For dairy products: I do not eliminate them but I consume them in moderation. Butter in small quantities is not a problem as part of a varied diet.