Fats, also called lipids (from the Greek lipos = fat) are a heterogeneous group of substances that have in common a low degree of solubility in water.
They are soluble in organic solvents such as benzene, ether or chloroform.
Fats are made of carbon, hydrogen, oxygen and carbohydrates, but the ratio of hydrogen to oxygen is much higher.
This characteristic makes them more energetic than carbohydrates in absolute terms but reduces their
energy efficiency with the same amount of oxygen consumed.
We mainly find them in foods of animal origin (fats) but are also abundantly present in the vegetable kingdom (oils).
Oils and fats are very similar chemically but, while the former are liquid at room temperature, the latter are solid.
There are over 500 types of fats, classified according to their molecular structure in simple compounds and derivatives:
They are the most abundant in our body (about 95%) and in our diet (about 98% of lipids present in food are ingested in this form).
They represent the main form of deposit and use. Among the best known are waxes and triglycerides.
Inside they are triglycerides combined with other chemicals such as phosphorus, nitrogen and sulphur. They represent about 10% of fats in our body.
Among the best known are phospholipids, glycolipids and lipoproteins.
Derived from the transformation of simple or compound lipids.
The most important is cholesterol, but also vitamin D, steroid hormones, palmitic, oleic and linoleic acid.
Triglycerides derive from the union of a molecule of glycerol with three fatty acids which are formed by hydrocarbon chains ranging from a minimum of 4 to a maximum of 20 carbon atoms.
The fatty acids may be saturated or unsaturated.
SATURATED FATTY ACIDS
Are free of double bonds and therefore have the maximum number of hydrogen atoms.
We mainly find them in products of animal origin (eggs, milk and derivatives) but also in food of vegetable origin (coconut and palm oil).
UNSATURATED FATTY ACIDS
Contain one (mono) or more (poly) double bonds between carbon and hydrogen atoms.
POLYUNSATURATED FATTY ACIDS
They contain over two bonds between the carbon atoms in fish, nuts, sunflower oil, corn oil and some plant extracts.
ESSENTIAL FATTY ACIDS
The human organism can not synthesise them; they are the precursors of prostaglandins, thromboxanes and leukotrienes, substances that intervene in the immune system, in the inflammatory response and influence the cardiovascular system.
HYDROGENATED FATTY ACIDS
Vegetables fatty acids origin are normally liquid at room temperature.
They can be solid by the hydrogenation process which alters their chemical structure, making them particularly harmful to our health.
In this way, we get the so-called trans or hydrogenated fatty acids.
Triglycerides are the form of fatty acid storage, like glycogen and glucose.
During the energy processes, our body breaks down the bond between glycerol and fatty acids by channelling them into two different metabolic pathways.
While glycerol is used to produce glucose, free fatty acids are transported into the bloodstream in association with albumin, a plasma protein that transports them to the muscles where they form the energy substrate for oxidative processes.