Introduction
The food which we take from various sources provides us energy and other substances the body needs. The food which we take contains three major nutrients and they are carbohydrate, fat, and protein. The body uses them as a source of energy for maintaining normal metabolic activities. We get carbohydrates from wheat, cereal crops, potatoes, peas, and other starchy vegetables, protein from meat, egg, pulses, etc., and fat from oilseeds, butter, cream, milk, etc.
Fat is also known as fatty acid and it is made up of three important elements: carbon, hydrogen, and oxygen, but the amount of carbon is in maximum quantity. It is an important macronutrient and is also an important part of the diet for all animals and humans. Body stores fat for protection, warmth, and energy. Different types of fats, which are, saturated and unsaturated, keep our body healthy in different ways.
It has been proven that not all types of fats are unhealthy and cause heart diseases. In fact, most fats are required in adequate amounts for normal bodily functions, especially brain functions. The amount of fat we eat doesn't impact our weight or our cholesterol or our risk of heart disease nearly as much as what kind of fat we eat.
Now, what is fat? Let's take a tour inside a salmon which is a fatty fish, past the organs, past the tissues, and into the cells. The stuff we call fat is actually made up of compact molecules called triglycerides, which are not similar in nature. There are three carbons on the left side of the cells, they are glycerol. They are usually the backbone that holds the rest of the molecule together. Now, there are three long chains on the right that are called fatty acids, and its subtle differences in the structures of these chains determine whether a fat is solid or liquid, whether it goes rancid quickly, and most importantly, how good or bad it is for you. Now, let’s examine the differences. One is length. Fatty acids can be short or long. Some fatty acids have only single bonds and some have double bonds.
Fatty acids with only single bonds are called saturated, and those with one or more double bonds are called unsaturated. For unsaturated fats, the double bond in these molecules has a weird property; they’re rigid. This brings us to think that there are two ways to arrange every double bond. The first is where both hydrogens are on the same side and both carbons are on the same side. The second way is that the hydrogens and carbons are on opposite sides of the double bond. Even though both of these molecules are made up of exactly the same building blocks, they are two different substances and function in dissimilar ways inside us. They do not turn sour and they are more stable during deep-frying. They can change the texture of food in ways that other fats just can’t. They are also terrible for your health even though technically they are a type of unsaturated fat.
Classification of Fats:
Based on various factors, fats are classified into various categories. They are:
Fats or Fatty Acids: These types of fat refer to any type of fat, but mostly, they are solid fats, which are in solid form at room temperature.
Lipids: This can refer to any type, regardless of whether it is liquid or solid.
Oils: They describe any fat that is liquid at room temperature.
Animal Fats: Among these are butter, cream, and fats in meats, such as lard.
Vegetable Fats: These are fats that are present in olives and avocados.
What are Trans Fats:
They are manufactured fats. They are products that add hydrogen to liquid vegetable oil to make them more solid in texture. They are also known as hydrogenated fats. Major examples of trans fats are cake, cookies, fried potatoes, potato chips, etc.
Essential Fats: There are so many fats that are synthesized by our body, but there are also fats that are taken through diet, and these types of fat are called essential fats as they are taken in an indirect way for the proper functioning of the body. Example: Linoleic, linolenic, and arachidonic acids.
FAQs on Fats
1. What are fats in the context of biology?
In biology, fats are a type of lipid, which are macromolecules essential for life. Chemically, they are triglycerides, meaning they are esters formed from one molecule of glycerol and three molecules of fatty acids. Fats are a major component of our diet and play a critical role in storing energy and supporting cellular functions.
2. What are the main types of dietary fats?
Dietary fats are primarily classified into four main types based on their chemical structure:
- Saturated Fats: Lack double bonds between the individual carbon atoms. They are typically solid at room temperature.
- Unsaturated Fats: Contain one or more double bonds in their fatty acid chains. They are usually liquid at room temperature and include monounsaturated and polyunsaturated fats.
- Monounsaturated Fats: Have one double bond in the fatty acid chain.
- Polyunsaturated Fats: Have more than one double bond. Omega-3 and Omega-6 are key examples.
- Trans Fats: Are created in an industrial process that adds hydrogen to liquid vegetable oils to make them more solid (hydrogenation).
3. What is the main difference between saturated and unsaturated fats?
The primary difference lies in their chemical structure, which affects their physical properties and health impact. The difference between saturated and unsaturated fats can be summarised as:
- Chemical Bonds: Saturated fats have no double bonds in their fatty acid tails, making their structure straight. Unsaturated fats have at least one double bond, which creates a 'kink' or bend in the molecule.
- Physical State: Due to their straight structure, saturated fats pack together tightly and are typically solid at room temperature (e.g., butter). The 'kinks' in unsaturated fats prevent tight packing, making them liquid at room temperature (e.g., olive oil).
- Sources: Saturated fats are common in animal products like meat and dairy, while unsaturated fats are found in plant sources like nuts, seeds, and vegetable oils.
4. What are the primary functions of fats in the human body?
Fats are crucial for several vital bodily functions beyond just being a component of food. Their key roles include:
- Energy Storage: Fats are the body's most concentrated source of energy, providing 9 calories per gram.
- Insulation: The layer of fat under the skin (adipose tissue) helps to insulate the body and maintain a stable temperature.
- Organ Protection: Fat deposits surround essential organs, providing a protective cushion against physical shock and injury.
- Hormone Production: Cholesterol, a type of lipid, is a precursor for producing steroid hormones like estrogen and testosterone.
- Vitamin Absorption: Fats are necessary for the absorption and transport of fat-soluble vitamins (A, D, E, and K).
5. What are some examples of foods containing healthy fats?
Healthy fats are primarily unsaturated fats, which are beneficial for heart health and overall well-being. Good food sources include:
- Monounsaturated Fats: Avocados, olive oil, canola oil, and nuts like almonds, cashews, and peanuts.
- Polyunsaturated Fats (Omega-3 and Omega-6): Fatty fish (salmon, mackerel, sardines), flaxseeds, chia seeds, walnuts, and sunflower oil.
Incorporating these foods into a balanced diet can help improve cholesterol levels and reduce the risk of cardiovascular disease.
6. What are trans fats and why are they considered unhealthy?
Trans fats, or trans-fatty acids, are a form of unsaturated fat. While small amounts occur naturally in some meat and dairy products, most are industrially produced through a process called hydrogenation, where hydrogen is added to vegetable oil. This process makes the oil more solid and stable. They are considered unhealthy because they raise your 'bad' (LDL) cholesterol levels and lower your 'good' (HDL) cholesterol levels, significantly increasing the risk of heart disease, stroke, and type 2 diabetes.
7. How are fats chemically different from carbohydrates, even though both provide energy?
While both are major energy sources, fats and carbohydrates have distinct chemical structures. Carbohydrates are polyhydroxy aldehydes or ketones, composed of long chains of sugar units (monosaccharides). Fats are triglycerides, which are esters of glycerol and fatty acids. This structural difference means fats are more reduced and contain less oxygen than carbohydrates, allowing them to store more than twice the energy per gram (9 kcal/g for fats vs. 4 kcal/g for carbs). The body uses carbs for quick energy and fats for long-term energy storage.
8. Why is consuming dietary fat essential for absorbing certain vitamins?
Consuming fat is essential because some vitamins are 'fat-soluble', meaning they dissolve in fat, not water. These are Vitamins A, D, E, and K. For the body to absorb these vitamins from the small intestine into the bloodstream, they must be transported along with fat molecules. Without dietary fat, the absorption of these crucial vitamins would be severely impaired, leading to deficiencies. This is a key example of the codependency of different nutrients. For more details, you can read about fat-soluble vitamins.
9. How does the body digest fats, given they are insoluble in water?
The digestion of fats is a multi-step process designed to overcome their insolubility in the watery environment of the digestive tract. The process of digestion of dietary fatty acids involves:
- Emulsification: In the small intestine, large fat globules are broken down into smaller droplets by bile salts produced by the liver. This process, called emulsification, increases the surface area for enzymes to act upon.
- Enzymatic Digestion: The enzyme lipase (primarily from the pancreas) then breaks down these small fat droplets into fatty acids and glycerol.
- Micelle Formation: The resulting fatty acids, glycerol, and other lipids aggregate with bile salts to form tiny spheres called micelles, which can transport the digested fat to the intestinal cells for absorption.
10. From a biological and chemical standpoint, what is the real difference between fats and oils?
Both fats and oils are chemically triglycerides, but the key difference is their physical state at room temperature, which is determined by the type of fatty acids they contain.
- Fats are typically solid at room temperature. This is because they have a high proportion of saturated fatty acids, whose straight-chain structures allow them to pack closely together.
- Oils are liquid at room temperature. This is due to a higher proportion of unsaturated fatty acids. The 'kinks' in their structure prevent them from packing tightly.
Essentially, an oil is just a fat that is liquid at room temperature. To learn more, see the difference between fat and oil.
11. Beyond energy storage, what other structural roles do lipids like fats play in our cells?
While energy storage is a primary function, lipids play a fundamental structural role. The most important is the formation of cell membranes. Phospholipids, a specific type of lipid, form the phospholipid bilayer that is the basic framework of all cell membranes. This bilayer is semi-permeable, controlling what enters and exits the cell. Additionally, lipids are components of myelin sheaths that insulate nerve cells, and they are integral to various signalling pathways within and between cells.
