The Truth Behind the Myth #3: Fats Make You Fat

"If you want to lose weight, stop eating fat." This advice has influenced generations. Since the 1980s, lipids have been accused of being the main culprits behind weight gain, high cholesterol, and cardiovascular diseases. As a result, many people avoid them, sometimes even radically.

But in reality, lipids are not your enemies. Their role is fundamental, and their link to weight gain is much more complex than it seems.

What are lipids?

Lipids are macronutrients, just like carbohydrates and proteins. They are the fats found in our diet, as well as in our bodies, in the form of energy reserves.

They fulfill several essential functions:

• Energy: Lipids are the most concentrated form of energy, with 9 kcal per gram (compared to 4 kcal for carbohydrates or proteins).
• Structure: They form cell membranes and ensure cell elasticity.
• Vitamin transport: Vitamins A, D, E, and K are fat-soluble, meaning they can only be absorbed in the presence of fats.
• Hormone production: Lipids are essential for the synthesis of many hormones, especially sex hormones.
• Protection: They protect vital organs by forming an insulating layer.
• Regulation: They participate in the regulation of inflammation and the immune system.

Lipids come in different families:

• Saturated fatty acids (found in butter, cheeses, meat, coconut oil),
• Monounsaturated fatty acids (olive oil, avocado, almonds),
• Polyunsaturated fatty acids (omega-3 and omega-6, found in fatty fish, flaxseeds, nuts),
• Trans fatty acids (industrial hydrogenated fats, very harmful).

The problem is therefore not fat itself, but the quality of the lipids consumed.

Why does this myth persist?

The myth that "fats make you fat" stems from several misconceptions:

• Their high caloric density (9 kcal/g) led to the belief that any fat consumption would immediately turn into body fat.
• Public health policies in the 1980s-1990s encouraged "low-fat" diets, without really distinguishing between good and bad fats.
• The food industry capitalized on this trend to sell products that were "light" in fat but rich in sugar or additives, further reinforcing the idea that "fat = bad."
• Finally, there is a frequent confusion between dietary fat and body fat, as if one automatically transforms into the other. This is false: gaining body fat results from an overall calorie surplus, not simply the presence of lipids.

What science says

Recent research shows that moderate or even high-fat diets are not associated with weight gain, provided that energy balance is respected and good fat sources are prioritized.

A study of 600 people over one year found no significant difference in weight loss between a low-carb (and thus high-fat) diet and a low-fat diet. What mattered most? The quality of food and portion management.

Moderate fat intake, particularly unsaturated fatty acids, is associated with better weight control and a reduced risk of cardiovascular disease.

Are all lipids created equal?

No, and therein lies the common mistake. We must differentiate between types of lipids:

Good lipids

• Omega-3 (EPA/DHA): anti-inflammatory, protective for the brain and heart.
• Monounsaturated fatty acids: good for the cardiovascular system.
• Dietary cholesterol (in moderation): necessary for hormone production.

Sources: olive oil, fatty fish, avocado, whole eggs, nuts, seeds…

Lipids to limit

• Trans fatty acids: industrially processed, associated with a high risk of heart disease.
• Excess saturated fatty acids: problematic if consumed in an unbalanced way (processed foods, cold cuts, snacks).

Lipids, satiety, and performance

Lipids also play a role in appetite control. They slow down digestion, which prolongs the feeling of satiety and helps prevent snacking. Moreover, they participate in hormonal regulation, energy production in endurance sports, and muscle recovery.

For women, insufficient fat intake can lead to hormonal imbalance, affecting the menstrual cycle, fertility, or bone density.

Key takeaways

Lipids are not the enemy of your waistline. They are essential nutrients, vital for overall health and balance of the body.
The myth that "fats make you fat" is based on a simplistic view of nutrition.

What makes you gain weight is a caloric excess. What protects your health is the quality of the lipids you consume.

Reintroducing good fats into a balanced diet is not only safe: it's a necessity.