Dietary Fats: Types, Roles, Health, and Recommended Intakes

What are fats, and what role do they play in the body?

Fats —or lipids—are macronutrients essential for the body’s functioning. Composed mainly of triglycerides (a combination of glycerol and three fatty acids), they perform vital functions: they serve as a concentrated source of energy (9 kcal/g), facilitate the absorption of the fat-soluble vitamins A, D, E, and K, mechanical protection of organs, thermal insulation, and the formation of cell membranes. Fatty acids are also essential hormone precursors, particularly for prostaglandins and steroid hormones. Essential fatty acids —which the body cannot synthesize—must be obtained through the diet.

What are the different types of dietary fats?

Dietary lipids are classified into four main groups based on their chemical structure:

• Saturated fats: solid at room temperature, found in butter, cream, fatty meats, and coconut and palm oils. In excess, they raise LDL cholesterol.
• Monounsaturated fats: liquid at room temperature, abundant in olive oil, avocados, and almonds. They have a neutral or beneficial effect on lipid profiles.
• Polyunsaturated fats: include omega-3s (fatty fish, flaxseeds, walnuts) and omega-6s (sunflower oil). Omega-3s are particularly well-documented for their anti-inflammatory and cardioprotective effects.
• Trans fats: derived from the industrial hydrogenation of vegetable oils, found in hard margarines and many ultra-processed foods. They raise LDL, lower HDL, and are associated with an increased risk of cardiovascular disease. The EFSA recommends limiting them as much as possible.

How do fats affect cardiovascular health?

The impact of fats on the cardiovascular system depends heavily on their type. Unsaturated fats—monounsaturated and polyunsaturated—help maintain a healthy lipid profile by lowering LDL and preserving HDL. Fish oils rich in EPA and DHA reduce blood triglycerides and have a documented antiplatelet effect. Conversely, a high intake of saturated and trans fats is associated with an increased risk of atherosclerosis, heart attack, and stroke. ANSES recommends that fats account for 35 to 40% of total energy intake, with less than 12% coming from saturated fats.

How much fat should you consume each day?

French nutritional guidelines (ANSES, 2016) set the optimal fat intake at 35% to 40% of daily energy intake. For an adult consuming 2,000 kcal/day, this amounts to approximately 78 to 89 g of fat. The recommended breakdown is:

• Saturated fats: less than 12% of total energy intake.
• Monounsaturated fats: about 15–20%.
• Polyunsaturated fats: 5–8%, with an omega-6 to omega-3 ratio ideally less than 5:1 to limit inflammation.

Stabilizing blood sugar levels by combining high-quality fats with complex carbohydrates optimizes the absorption of fat-soluble vitamins and reduces insulin spikes.

Do dietary fats really cause weight gain?

Contrary to a persistent misconception, dietary fats are not directly responsible for weight gain. It is the overall calorie surplus—regardless of its source—that promotes fat storage. Studies show that diets containing a moderate amount of unsaturated fats are at least as effective for sustainable weight loss as very low-fat diets, particularly because fats prolong feelings of fullness and reduce cravings. A well-designed weight-loss diet does not eliminate fats but selects the best sources while limiting saturated and trans fats.

How can you incorporate healthy fats into your diet?

A few simple habits can help optimize your intake of high-quality fats:

• Use extra-virgin olive oil for dressings and canola oil for gentle cooking.
• Eat fatty fish (salmon, mackerel, sardines) two to three times a week for the long-chain omega-3s EPA and DHA.
• Include nuts (almonds, walnuts, hazelnuts) as snacks: they’re rich in unsaturated fats, fiber, and micronutrients.
• Limit ultra-processed foods and check labels for partially hydrogenated fats.

These choices promote healthy lipid metabolism, support cognitive health—polyunsaturated fatty acids help maintain the fluidity of neuronal membranes—and are part of a lifestyle that supports weight management and long-term cardiovascular health.