Fats or Lipids

Fat or Lipid can be defined as:

1. Any of a group of organic compounds that are greasy to the touch, insoluble in water, and soluble in alcohol and ether: lipids comprise the fats and other esters with analogous properties and constitute, with proteins and carbohydrates, the chief structural components of living cells.

2. Any of a group of organic compounds, including the fats, oils, waxes, sterols, and triglycerides, that are insoluble in water but soluble in nonpolar organic solvents, are oily to the touch, and together with carbohydrates and proteins constitute the principal structural material of living cells. (American Heritage Dictionary).

Lipid is a substance that is greasy, insoluble in water but soluble in organic substances and constitute the principal structural material of living cells together with carbohydrate and protein.

The main functions of lipid are?

1. They serve as structural components of biological membranes.
2. They provide energy reserves, predominantly in the form of triacylglycerols / triglycerides.
3. Both lipids and lipid derivatives serve as vitamins and hormones.
4. Lipophilic bile acids aid in lipid solubilization.

Lipids are grouped in 4 main division:

-Triacylglycerides
-Phospholipids
-Plasmalogens
-Sphingolipids

Lipids play diverse and important roles in nutrition and health. Many lipids are absolutely essential for life, however, there is also considerable awareness that abnormal levels of certain lipids, particularly cholesterol (in hypercholesterolemia) and, more recently, fatty acids with trans fatty acids, are risk factors for heart disease amongst others.

We need fats in our bodies and certain types in our diet. Animals in general use fat for energy storage because fat stores 9 KCal/g of energy. Plants, which do not require energy for movement, can afford to store food for energy in a less compact but more easily accessible form, so they have evolved use starch (a carbohydrate, not a lipid) for energy storage.

Furthermore, lipids can be stored in an anhydrous form whereas carbohydrates typically cannot, which means that anhydrous lipid stores about 6 times as much energy per weight as hydrated carbohydrates. As an example, a typical 70 kg man would have to weigh approximately 125 kg if his energy stores were converted from triacylglycerol to glycogen.

One need not think that fat and lipids are the same thing this is because fat is actually is a subgroup
of lipid.

So here we will discuss fat or fatty acids more as this has the more impact on human body and health.

Fatty acids fill two major roles in the body:
1. as the components of more complex membrane lipids.
2. as the major components of stored fat in the form of triacylglycerols / triglycerides.

Chemically, fatty acids can be described as long-chain monocarboxylic acids the saturated examples of which have a general structure of CH3(CH2)nCOOH. The length of the chain usually ranges from 12 to 24, always with an even number of carbon atoms. When the carbon chain contains no double bonds, it is a saturated chain. If it contains one or more such bonds, it is unsaturated. The presence of double bonds reduces the melting point of fatty acids.

So points that you should know Saturated Fatty acids contains NO double bonds, Unsaturated Fatty acids have double bonds, this makes the difference because the presence of double bonds appear to lower the melting points of lipids and makes the lipid easier to disintegrate (metabolised). Therefore, unsaturated fatty acids are Healthier!

Our bodies can make its own fats, except these two type of fats which are the highly unsaturated fatty acids know as linoleic acid and linolenic acid - which are called essential fatty acids. 

Fatty acids are stored for future use as triacylglycerols in all cells, but primarily in adipocytes of adipose tissue. Triacylglycerols constitute molecules of glycerol to which three fatty acids have been esterified. The fatty acids present in triacylglycerols are predominantly saturated. The major building blocks for the synthesis of triacylglycerols, in tissues other than adipose tissue, is glycerol.

Fats eaten by human will be metabolised to give energy. In fact, fats are the MAIN source of energy and acts as insulator of heat. This explains why a fatter person tends to feel more at ease in cold situation.

Unused fats will be deposited or stored in the skin, the covering of the heart, the inner lining of blood vessels among others. and this pose health complication if the deposit exceeds normal level.

One thing to note, fatty acids can be made up from Acetyl-coA. Acetyl-CoA is the end product of carbohydrate metabolism. Therefore, even though one eats sweets or simple sugar instead of other heavy carbohydrates or fats fat can still be produced from simple sugar byproducts.

HEALTH EFFECTS DUE TO EXCESSIVE FAT

Cholesterol is a blood fat needed by the body in moderate amounts. However, high cholesterol levels can lead to atherosclerosis and coronary artery disease (CAD) which include Stroke, heart attack which is caused by blood vessels or capillary obstruction. Angina is chest pain caused by the restriction of blood flow to the heart (cardiac ischemia).

Two types of lipoproteins transport cholesterol throughout the body:

LDL (low-density lipoprotein), “bad” cholesterol), makes up most of your body’s cholesterol. High levels of LDL cholesterol increase the risk for heart disease and stroke.

HDL (high-density lipoprotein), (“good” cholesterol), absorbs cholesterol and carries it back to the liver. The liver then discards it from the body. High levels of HDL cholesterol decrease the risk for heart disease and stroke.

The healthy range of boy fats depends of your age, but for a women it is 21 – 36%, and for men 12 – 25%.



Reference:
https://www.cdc.gov/cholesterol/ldl_hdl.htm
https://tanita.eu/blog/healthy-body-fat-percentage/