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What Are Lipids?
What is a lipid?
A lipid is a naturally occurring organic molecule found in all living organisms, characterised by its insolubility in water and solubility in fats and organic solvents. The term comes from the Greek lipos — fat.
In everyday language, lipids are called "fats." But this word reduces them to their energy-storage role, obscuring their structural and regulatory functions — which are, for human health, far more significant.
Lipids are not your enemy. They are the architects of your biology.
What are the different types of lipids?
The main types of lipids in the human body are fatty acids, triglycerides, phospholipids, cholesterol, and ceramides. Each fulfils a distinct biological role — structural, energetic, hormonal, or protective.
Fatty acids
Fatty acids are the basic units of most lipids. They are divided into three categories according to their molecular structure:
- Saturated fatty acids — straight chains, pack tightly, produce a more rigid cell membrane structure. Found in butter, fatty meats, coconut oil, and palm oil.
- Monounsaturated fatty acids — one double bond in the chain. Found in olive oil, avocado, and almonds.
- Polyunsaturated fatty acids — multiple double bonds, give fluidity to cell membranes. Include omega-3 and omega-6 — the most important for metabolic and skin health.
Triglycerides
Three fatty acids attached to a glycerol molecule. The principal storage form of fat in adipose tissue and in the blood. Triglyceride levels are one of the markers on your lipid panel.
Phospholipids
Two fatty acids and a phosphate group attached to glycerol. The major constituents of all cell membranes — they form the lipid bilayer that surrounds every cell in the human body.
Cholesterol
A lipid from the sterol family. It is not a fatty acid — it has a cyclic molecular structure. Cholesterol is an essential component of cell membranes, and the precursor to steroid hormones (including estrogen and testosterone), vitamin D, and bile acids. Approximately 75 to 80% is produced by the liver; the rest comes from diet.
Ceramides
Complex lipids composed of a fatty acid linked to sphingosine. They constitute approximately 50% of the lipids in the stratum corneum — the outermost layer of the epidermis — and play a central role in skin barrier cohesion and impermeability.
What do lipids do in the body?
Lipids fulfil four essential biological functions: building cell membranes, storing and producing energy, regulating hormonal signalling, and protecting the skin barrier. Without lipids, no cell can exist or function.
1. Cell membrane structure
Every cell in the human body is surrounded by a lipid membrane — the phospholipid bilayer. Without lipids, there is no cell. Without cells, no life. Polyunsaturated fatty acids — particularly omega-3 — influence the fluidity of this membrane, meaning the ability of proteins and signalling molecules to move and function correctly within it.
2. Energy storage and production
Triglycerides stored in adipose tissue constitute the body's most energy-dense reserve — approximately 9 calories per gram, compared to 4 for carbohydrates and proteins.
3. Hormonal signalling and regulation
Cholesterol is the precursor to all steroid hormones — estrogen, testosterone, cortisol, aldosterone, vitamin D. Without cholesterol, these hormones cannot be synthesised. Polyunsaturated fatty acids also participate in the production of prostaglandins, molecules involved in the regulation of inflammation.
4. Protection and barrier function
In the skin, lipids — ceramides, cutaneous cholesterol, free fatty acids — form the lipid matrix of the skin barrier. This barrier regulates transepidermal water loss, protects against pathogens and pollutants, and maintains the structural integrity of the skin.
Lipids and cholesterol: what is the relationship?
Cholesterol is a lipid — but it is not a dietary fat in the conventional sense. It is a structural molecule produced primarily by the liver.
Your lipid panel measures several markers:
- LDL (low-density lipoprotein) — cholesterol transporter from the liver to tissues
- HDL (high-density lipoprotein) — cholesterol transporter from tissues back to the liver for elimination
- Triglycerides — fats circulating in the blood after meals or released from fat reserves
- Total cholesterol — the sum of all fractions
What your lipid panel reveals is the state of your lipid metabolism — the way your body produces, transports and eliminates lipids. This metabolism is influenced by diet, physical activity, genetics, and hormones — particularly estrogen, which regulates the activity of hepatic LDL receptors.
What is the role of lipids in skin?
The skin is the body's most visible lipid organ. Its outermost layer — the stratum corneum — is composed of approximately 50% ceramides, 25% cutaneous cholesterol, and 15% free fatty acids, three lipids that together form the barrier retaining moisture and protecting against external aggressors.
The stratum corneum — the superficial layer of the epidermis — is a lipid structure organised in lamellae. It is composed of approximately:
- 50% ceramides
- 25% cutaneous cholesterol
- 15% free fatty acids
These three lipids together form the matrix that retains moisture and protects against external aggressors. When this matrix is intact, the skin is supple, comfortable, resilient. When it is deficient, the skin becomes dry, tight, sensitive — and no moisturising cream can durably compensate for this deficit, because water does not replace lipids.
Essential fatty acids — ALA omega-3 and linoleic acid omega-6 — are direct components of this matrix. They cannot be synthesised by the body and must be provided through diet or skincare.
Which lipids can the body not produce itself?
The two essential fatty acids the human body cannot synthesise are ALA (alpha-linolenic acid, omega-3) and linoleic acid (omega-6). Both must be obtained through diet or topical skincare — and both are direct structural components of the skin barrier.
Alpha-linolenic acid (ALA) — plant omega-3, precursor to EPA and DHA. Found in flaxseed, chia, walnuts, and in maximum concentration in sacha inchi oil (44 to 54% of composition). In the European Union, ALA is recognised by EFSA for contributing to the maintenance of normal blood cholesterol levels at a daily intake of 2g (EU Regulation 432/2012).
Linoleic acid (LA) — omega-6, precursor to arachidonic acid. A major structural component of the skin barrier. A deficiency in linoleic acid is one of the documented causes of skin barrier weakening.
These two essential fatty acids are at the heart of Dafee's philosophy — provided internally by Daily-Feed, and externally by Daily-Feel.
→ Complete guides: Omega-3 Fatty Acids · Sacha Inchi Oil · How to Read Your Cholesterol Results · What Damages the Skin Lipid Barrier?
Written by the Dafee Science Team — published 05/06/2026. Dafeepédia content is developed from European regulatory sources (EFSA, EC Regulation 432/2012) and peer-reviewed scientific literature, and reviewed for accuracy before publication.
The Dafee Metabolic Intelligence app interprets standard lipid blood panels as metabolic patterns rather than isolated thresholds — available at app.dafee.fr.