Fats are one of the essential parts of the diet and play a crucial role in metabolism. It is a type of macronutrient along with protein and carbohydrates. On the other hand, a calorie is a unit of energy, generally measured in kilocalories. In the following sections, you will learn more about fats and calories. 

Calories

As mentioned before, a calorie is a unit of energy. It is generally measured in kilocalories. Kilocalories can be defined as the amount of heat required to increase water temperature by 1 °C. Calories are not the ingredients of food. Rather, it is only a measurement of energy. It indicates the energy obtained from the food or fuel during its metabolism or consumption. A one-gram calorie is equal to 4.1840 joules. 

Fats

Fats are organic compounds with a glycerol backbone, which has three fatty acid groups. As a type of macronutrient along with protein and carbohydrates, the consumption of fat in our body produces energy essential for survival. They have the highest energy storage compared to proteins or other macronutrients. 

Fats are chemically stable in nature. It also serves other important functions like maintaining the cell membrane, working as hormones, and temperature maintenance. In terms of energy, one gram of fat can provide nine calories of energy.

The primary function of fats in the body is to act as a storage mechanism for energy and a source of reserve energy. During low food intake, fat stores in the body may be mobilised and broken down to release energy, allowing the body to save energy. Moreover, fats act as an insulating layer, which helps keep the body’s heat in check. This layer protects the internal organs, particularly vulnerable to physical injury. 

It is possible to transform dietary fats into other lipids, which serve as the primary structural substance in the membranes that surround our cells. Fats also help in absorbing vitamins in the bloodstream. Fatty acids are also employed in producing several steroids and hormones, which are essential in regulating appropriate tissue development and maintenance.

Types of Fats

Fats can be categorised into four types:

• Saturated Fats: Fats that contain glycerol and fully saturated fatty acids chain are known as saturated fats. In the case of saturated carbons, this means that they have all been sp3 hybridised, with two hydrogen atoms covalently bound to each carbon in the backbone. This fat viscosity and energy content class are greater than those of their unsaturated siblings. 

Due to low solubility, this kind of fat is one of the most typically connected with heart disease and arteriosclerosis in the general population (hardening of the arteries). Butter, coconut oil, pork, peanut butter, and cheese are examples of foods high in saturated fats.

• Monounsaturated Fats: The fat which contains only one double bond having two sp2 carbons in the alkyl chain of fatty acid is known as Monounsaturated fat. Peanuts, olives, and olive oil are all sources of monounsaturated fats, which are considered good fats. It is essential in the protection of the heart and is also involved in the maintenance of insulin sensitivity, fat storage, weight reduction, and maintaining normal energy levels in humans. The letter ω denotes the location of a triglyceride’s unsaturation or unsaturations. Olive oil is an example of monounsaturated fat.
• Polyunsaturated Fats: These are the fats that contain more than one double bond in the alkyl chain of fatty acid having more than two sp2 carbons. Polyunsaturated fats, such as Omega-3 and Omega-6 fatty acids, are important examples of polyunsaturated fats. 

Omega-3 aids in the reduction of inflammation and the maintenance of healthy hormone levels and cell membranes. When it comes to maintaining healthy brain and muscle function, Omega-6 fatty acids play a crucial role. They are found in abundance in corn, grapeseed, and sunflower oils.

• Trans Fats: Unsaturated fats have a large number of double bonds. Trans fat is defined as fat in which the conformation of the double bond is trans, as compared to other fats. Due to the superior packing and interaction with solvents of cis fats, trans fats are less soluble than cis fats. Their metabolism is, on the other hand, not easily accomplished by cellular machinery. 

Generally speaking, naturally occurring lipids are in the cis form. Isomerisation occurs during the partial hydrogenation of unsaturated lipids, which leads to the conversion of certain cis double bonds into trans double bonds. A naturally occurring trans-fatty acid, conjugated linoleic acid (CLA), has been demonstrated to be effective in boosting the immune system as well as preventing cancer from progressing. At room temperature, the cis double bond creates an inward bend, or ‘kink’, that prevents the fatty acids from clustering closely together, allowing them to remain liquid.

Essential Fatty Acids

The fatty acids that cannot be produced by our body but are necessary for it to function properly are known as essential fatty acids. For example, linoleic acid, Omega-3 fatty acids. They help in the regulation of hormones and many cellular functions. 

Conclusion

Fats are one of the macronutrients along with proteins and carbohydrates. They produce more energy or more calorific value than other macronutrients. Fats serve important functions: maintain the cell membrane, work as hormones, temperature maintenance, provide an insulation layer which cushions internal organs etc. There are four types of fats: saturated fats, monounsaturated fats, polyunsaturated fats, and trans fats. The difference between saturated and unsaturated fats have also been discussed with examples. Essential fatty acids are fats essential for the body to perform normally, aiding in the regulation of hormones and cellular functions.