Fats and Lipids: are they the same thing?
The lipids introduced with food are, in the vast majority of cases (> 90%), represented by triglycerides. In addition to these molecules, also called triacylglycerols, in commonly used foods we can also find a small amount of cholesterol, cholesterol esters, phospholipids and free fatty acids.
A CURIOSITY: although used as such, the terms "fat" and "lipid" are not synonymous. The fats are in fact represented by triglycerides only, while the term lipid includes, in addition to the aforementioned, also cholesterol, phospholipids and many other substances soluble in organic solvents but little or not soluble in water (terpenes, steroids, sphingolipids, waxes, etc.) .
Fatty acids can be distinguished as saturated or unsaturated, depending on the presence or absence of double bonds between the various carbon units. When these are absent the fatty acid is called saturated; otherwise, we talk about unsaturated fatty acids. The latter, in turn, are divided into monounsaturated, when they have a single double bond, and polyunsaturated, when they contain two or more double bonds.
The presence of unsaturated fatty acids lowers the melting temperature of the triglyceride; for this reason the oils are liquid at room temperature. Triglycerides which, like those contained in butter, are solid in the same conditions, are instead called fats.
Most of the fatty acids present in the body are contained in triglycerides, phospholipids and cholesterol esters. These lipid molecules are transported in the plasma by lipoproteins. There is also a small proportion of free fatty acids, which in the circulatory stream is conveyed by albumin.
Triglycerides (TG) are also called neutral fats, because the three fatty acids that constitute them commit the carboxyl group to the bond, thus losing their negative charge.
Dietary lipid functions
Lipids cover many functions:
they are a concentrated source of energy (in fact, one gram of lipids provides 9Kcal, more than twice those provided by carbohydrates and proteins).
They convey the fat-soluble vitamins (also for this reason it is dangerous to excessively lower the intake of dietary fat; in fact, if the diet is permanently and extremely low in fat, you can run into important vitamin deficiencies);
They make essential fatty acids (AGE), which are very important because they must necessarily be introduced with the diet.
They act on satiety in the long term, delaying the onset of hunger; lipids are in fact a real concentration of energy, distributed in an extremely small volume; for this reason, you risk taking many calories before feeling full. However, thanks to their high energy charge, over time they tend to postpone the need to take food again.
The lipids are therefore not very satiating in the immediate, but they act on the satiety in the long term, delaying the onset of the new stimulus of the hunger.
Functions of lipids in the body
The body's adipose deposits are formed by triglycerides accumulated inside the adipocytes in liquid form, since the body temperature exceeds their melting point.
The triglycerides contained in adipose tissue are the body's main energy reserve.
Fat-soluble vitamins accumulate.
Adipose deposits protect from trauma and shape the body shape.
They work as thermal insulators and, if necessary, can be metabolized to produce heat (brown adipose tissue).
Lipids have a structural function (cell membranes, myelin, hydrolipidic film).
They also possess metabolic functions (cholesterol is a precursor of various molecules; AGEs are precursors of eicosanoids).
To know more:
Cholesterol
Omega3 and omega6 fatty acids
Fats and health
