What are lipids? | The nutrition guide

They're the arch-enemy of beauty magazines and numerous food manufacturers that extol the virtues of “fat-free" foods. But do you actually know what lipids do?

What are lipids? | The nutrition guide

To grow, survive and thrive, our bodies need three macronutrients: carbohydrates, protein, and fat. These three elements are all necessary, even though some of them are given the cold shoulder, as is often the case with lipids. 

With summer coming and people encouraged to shed those "shameful" curves, the finger is often pointed at fats.
But why then are they one of the three basic elements of a healthy, balanced diet?

What are they for? How can you tell good fat from bad fat, and where can you find it? Read on to learn all you need to know about lipids! 

What are lipids?

The term "lipids" might not mean anything to you, but you'll certainly know them by their other name: "fats".
These molecules, composed of fatty acids (triglycerides), are part of the macronutrients family, along with protein and carbohydrates.
Lipids are found in all our cells, including our brains, which are 70% fat!
They play a central role in making sure our bodies work properly. 

Lipids and cholesterol

The body is naturally composed of cholesterol, which is made by the liver and which we also eat in food.
We've all heard about the two types of cholesterol:
HDL (high-density lipoprotein), the "good" cholesterol;
LDL (low-density lipoprotein), also referred to as "bad" cholesterol.

These are the particles that carry cholesterol around our bodies. In the case of HDL, the cholesterol is carried to the liver for excretion. For LDL, the cholesterol is transported to the cells, where it will be stored. In the case of LDL, it can build up in the blood, form deposits and block the arteries. Hence its bad reputation.

We often demonise cholesterol and therefore fats in general. But they're important and, as with anything else, quality and quantity are the keys to good health! For example, processed foods will be rich in bad cholesterol, while naturally fat-rich foods are essential for our bodies to function.

The 4 main roles of lipids

As with protein and carbohydrates, lipids play more than one role. They're the nutrient with the highest energy value. This makes them an excellent source of energy, providing 9 kcal per 1 g of fat. They also play an essential role within the body by forming cell membranes and allowing them to function (hormones, vitamins, reserves, transport, etc.). By definition they're hydrophobic, which means they don't dissolve in water.
Lipids therefore play a role in:

Providing energy

This is their main role. They provide energy through their storage capacity. Our fat reserves are stored in the form of adipose tissue, which can hold more than 80,000 calories!
This is how they provide the fuel our bodies need to move, think and grow. They take over this role from carbohydrates during a long bout of exercise. 

Building our bodies

Fats are what all cell membranes are made from. They also make up more than 70% of the white matter in our brains.
All our cells need fat in order to function and replace themselves each day. Fat also enables us to synthesise certain micronutrients, such as vitamin A, vitamin E, vitamin D and vitamin K, which are fat-soluble. They need fat to carry them around the body.


Fats also contribute to the production and synthesis of sex hormones and steroids. They're essential for our brains, our hearts, our arteries and our reproductive organs.
With their very active hormonal cycle, women can't do without fats!

Providing taste

Last but by no means least, fats give foods their creamy texture and accentuate their taste.

Absorption of lipids

In the mouth

The digestion of fat begins in the mouth, but with a limited effect because there are no enzymes in saliva that are capable of pre-digesting it. It's actually the process of chewing and the presence of protein that kick-start the digestion of fat.
So to digest fat properly, it's important to eat protein at the same time. 

In the stomach

This mixing is continued, and an enzyme starts to separate the triglycerides. A fat-rich meal will lead to the stomach emptying more slowly and more gastric juices being produced. This is why you often feel so sluggish after a very heavy, fatty meal.

In the small intestine

This is where most of the triglycerides will be broken down, through the action of bile and the pancreatic enzymes. At this stage, fatty acids are released that pass through the wall of the intestine to be carried either to the muscles to provide energy, or to adipose tissue in the form of fat reserves. 

The different families of fat

Fats or triglycerides are composed of saturated and unsaturated fats, which each have very specific physiological roles and therefore different effects on our health.

Saturated fats

Saturated fats are renowned for being harmful to our cardiovascular systems. They're mainly of animal origin:
deli meats;
dairy products. 

Unsaturated fats

Unsaturated fats are essential for the functioning of our brain cells' membranes. They also go by the names of mono- and polyunsaturated fatty acids.
They protect our arteries, reduce bad cholesterol, and protect us from cardiovascular disease.

All about omegas

Omegas are essential unsaturated fatty acids that the body absolutely needs in order to function, but that it can't synthesise by itself. A bit like the case of amino acids in protein.

The body uses these fatty acids to make other fatty compounds and various substances that are involved in vital biological functions, from blood clotting to inflammation, and immunity.

It's recommended that we consume plenty of omega-3 and omega-6, and that we have them in a ratio of 5:1 (omega-6 to omega-3) rather than the 10:1 ratio we tend to eat.  In other words, we currently undereat omega-3 and overeat omega-6. 

Here are some ways to increase omega-3 consumption:
* eat more vegetable oils that are rich in omega-3, such as linseed, walnut, hemp and rapeseed;
* eat more fish: once or twice a week;
* make sure your livestock is eating the right things. For example, if you change a chicken's diet by giving it linseed, you'll get eggs that are richer in omega-3!

The dangers of fat

Although fats are very important in our diets, you need the right balance. As they say, "you can have too much of a good thing”. Overconsumption of fats, in particular bad fats such as saturates, is a recipe for cardiovascular disease.
It's best to limit consumption or even avoid them altogether.

Tip: prioritise plant-based fatty acids (unsaturated fats) or those from fish over those in meat, which is rich in saturated fat.

Check out our article on healthy alternatives to fat to discover some great ideas for good fats you can eat without feeling guilty or short-changed!

Fat-free foods

No! We're not talking about processed foods marketed as "fat-free", but real foods that are naturally lacking in fat.

Foods containing no fats include:
* spices;
* fresh fruit and veg, although some are very high in sugar (e.g. sugar, honey, agave syrup, fruit-based sweets, sugary drinks, fizzy drinks).

Foods rich in fats

Our diets provide on average 80 g of fat per day. Lipids are mainly present in oil, butter, fat, some meat, fish, cheese, nuts and seeds.
The most fat-rich foods are vegetable oils and cod liver oil. They contain 100 g of fat per 100 g. This is the case no matter which type of oil you're talking about.

Here's a list of foods showing their fat content (given in grams per 100 g):
* Rapeseed, avocado, cod liver, hazelnut, walnut, sunflower, fish, olive oil: 100 g
* Lard: 100 g
* Duck or goose fat: 99.8 g
* Margarine (80% fat) and bread: 84.4 g
* Unsalted butter: 82.2 g
* Mayo with sunflower oil: 79.3 g
* Coconut: 65.1 g
* Almonds: 65.1 g
* Walnuts: 63.8 g
* Hazelnuts: 63 g

Fats are often demonised, yet they're as essential to our health as carbohydrates and protein. Provided that we eat enough good-quality ones and in moderation! So have you made your peace with fat?

What are fats? | The nutrition guide


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