Good fats: a guide to dietary lipids

Lipids (or fats) are one of the three essential macronutrients, alongside proteins and carbohydrates. Long demonized, they are nonetheless indispensable for the proper functioning of the body.

Their roles are multiple and fundamental. Fats are first and foremost a concentrated energy source, 9 kcal per gram, compared to 4 for carbohydrates and proteins. They are an essential component of cell membranes and serve as precursors to steroid hormones (testosterone, estrogens, cortisol). Without them, the body cannot absorb fat-soluble vitamins A, D, E, and K. The brain, composed of 60% fat, a large portion of which is omega-3, depends on them directly. Finally, through essential fatty acids, fats participate in the regulation of inflammatory processes.

In terms of quantity, fats should represent 35 to 40% of total caloric intake. For an adult consuming 2,000 kcal/day, this corresponds to 78 to 89 g of fat per day. But beyond quantity, quality matters most: not all fats have the same impact on health.

Saturated fats are solid at room temperature. They are called "saturated" because their carbon chains contain no double bonds. They are found primarily in animal products: butter, cream, cheese, fatty meats (lamb, pork, fatty beef), cold cuts, and processed foods. Coconut oil and palm oil are also rich sources.

Consumed in excess, saturated fats raise LDL cholesterol (the "bad" kind), promote arterial deposits, increase cardiovascular risk, and can reduce insulin sensitivity. This is why nutritional guidelines recommend limiting them to less than 12% of total caloric intake, fewer than 27 g per day on a 2,000 kcal diet.

In practice, this means replacing butter with vegetable oils rich in unsaturated fatty acids (olive, canola), and choosing lean meats and low-fat dairy products. Moderate consumption of saturated fats as part of an overall balanced diet is not dangerous, it is excess that is the problem.

Unsaturated fats are liquid at room temperature and are divided into two main categories based on their chemical structure.

Monounsaturated fats (omega-9) have a single double bond in their carbon chain. Oleic acid in olive oil is the prime example. They reduce LDL cholesterol while maintaining HDL ("good cholesterol").

Polyunsaturated fats (omega-3 and omega-6) have multiple double bonds. These are essential fatty acids: the body cannot synthesize them, so they must come from diet. Omega-3s include alpha-linolenic acid (ALA), EPA, and DHA; omega-6s include linoleic acid (LA).

Prioritizing unsaturated fats delivers multiple benefits: reduced cardiovascular risk, anti-inflammatory effects from omega-3s, improved blood lipid profile, and support for brain function. The ideal approach is to replace saturated and trans fats with unsaturated fats, rather than simply cutting total fat intake.

Omega-3s are essential polyunsaturated fatty acids with particularly beneficial health effects. Three main types exist: ALA (alpha-linolenic acid), plant-based, which serves as a precursor to the other omega-3s; EPA (eicosapentaenoic acid), with anti-inflammatory and heart-protective properties; and DHA (docosahexaenoic acid), essential for the brain and vision.

Their benefits span multiple dimensions. For the heart, they reduce triglycerides, prevent arrhythmias, and thin the blood. For the brain, they support memory, concentration, and help prevent cognitive decline. DHA is a major component of the retina, and positive associations have been found with reduced symptoms of depression.

The best food sources are fatty fish: salmon (2.2 g/100 g), mackerel (2.5 g), sardines (1.5 g), and herring (1.7 g). On the plant side, flaxseed oil is the most concentrated at 53 g of ALA per 100 g, followed by chia seeds (17.8 g), canola oil (9.1 g), and walnuts (6.8 g).

The recommended daily intake is 1.1 g/day of ALA for women and 1.6 g/day for men, along with 250–500 mg/day of EPA + DHA. In practice, two servings of fatty fish per week generally covers EPA and DHA needs.

Omega-6s are also essential polyunsaturated fatty acids, but their ratio to omega-3 matters as much as their absolute intake. In modern Western diets, this ratio often reaches 15:1 to 20:1, while the recommended optimal ratio is 4:1 to 5:1 at most. Excess omega-6 promotes inflammation and can neutralize the beneficial effects of omega-3.

The main sources of omega-6 are sunflower oil (63 g/100 g), corn oil (58 g/100 g), and soybean oil (51 g/100 g), ubiquitous in processed foods and margarines. Intensively farmed meats, fed on grains, are also high in omega-6. Arachidonic acid (AA), an omega-6 derivative found in fatty meats, eggs, and dairy products, is pro-inflammatory at high doses.

To rebalance this ratio, reduce sunflower and corn oils in favor of olive oil and canola oil, increase consumption of fatty fish, limit ultra-processed products, and choose eggs and meats from grass-fed animals, which have a better omega-3/omega-6 ratio.

Omega-9s are monounsaturated fatty acids. Unlike omega-3 and omega-6, the body can synthesize them, but dietary intake still provides meaningful benefits. Oleic acid is the standout, the main component of olive oil and the most common monounsaturated fatty acid in our diet.

Their benefits include reducing LDL cholesterol without lowering HDL, improving insulin sensitivity, a mild anti-inflammatory effect, and promoting the absorption of fat-soluble vitamins A, D, E, and K. Studies on the Mediterranean diet associate them with better longevity.

The richest source is olive oil at 73 g of oleic acid per 100 g. High levels are also found in hazelnuts (46 g/100 g), almonds (32 g/100 g), avocado oil (70 g/100 g), canola oil (62 g/100 g, also rich in omega-3), and avocado (9.8 g/100 g), which also provides fiber and potassium. Extra virgin olive oil, cold-pressed, is the best option: it retains its antioxidant polyphenols and vitamins. Prioritize it for dressings and gentle cooking (below 356°F / 180°C).

Trans fats (or trans fatty acids) are the most harmful to cardiovascular health. They are created during the hydrogenation of vegetable oils, an industrial process that solidifies liquid oils. Their danger stems from a dual harmful effect: they raise LDL cholesterol ("bad") while lowering HDL ("good"), promote systemic inflammation, and significantly increase the risk of cardiovascular disease, stroke, type 2 diabetes, and certain cancers.

They are found primarily in hydrogenated margarines (older formulations), industrial biscuits and pastries, chips and industrially fried snacks, ready meals, and fast food. On labels, they hide behind terms such as "partially hydrogenated fats," "partially hydrogenated oils," "shortening," or "hydrogenated vegetable fat."

Since 2021 in Europe, industrial trans fat content is limited to 2 g per 100 g of fat in foods. Some countries, the US and Denmark, have banned them entirely. When in doubt, always read the labels on processed products: even in small quantities, trans fats accumulate and have harmful long-term effects.

The quality of fats consumed during the eating window of intermittent fasting has a direct impact on the benefits of fasting.

During fasting hours, the body switches to fat-burning mode (lipolysis) and preferentially oxidizes available fatty acids, particularly stored triglycerides. Having good-quality fat reserves enables better energy production during this phase.

For breaking the fast, certain foods are particularly well suited. Avocado, rich in omega-9 and fiber, provides excellent satiety and gently reopens the eating window. Eggs supply a complete source of amino acids and balanced lipids. Fatty fish immediately deliver EPA and DHA for the brain and inflammation regulation. Walnuts and almonds combine omega-3, omega-9, and plant protein. Conversely, trans fats (industrial cookies, pastries) and excess saturated fats should be avoided during the eating window: they cancel out the anti-inflammatory benefits of fasting and promote post-meal inflammation.

For practitioners of extended fasting or the ketogenic diet, fats become the primary energy source. In this case, prioritizing quality fats, olive oil, coconut oil, clarified butter, ensures healthy ketosis. To learn more about the balance between macronutrients, check out our

The information presented in this guide is provided for educational and informational purposes only. It does not constitute personalized medical advice.

Fat needs vary according to age, sex, health status, and physical activity level. Consult a doctor or dietitian if you have a history of cardiovascular disease, high cholesterol, or diabetes; if you take lipid-lowering medications (statins); if you wish to follow a very low-fat or very high-fat diet (ketogenic); or if you are pregnant or breastfeeding.

These recommendations are based on data from the WHO (World Health Organization), EFSA (European Food Safety Authority), and the American Heart Association.