Macronutrients, as the name suggests, are nutrients that our body requires in a major proportion. These are the energy-yielding and building substances of our body and are broadly classified as Carbohydrates, Fats and Proteins.

The energy-giving capacity of these three macronutrients (expressed as calories) varies. Calories are needed to provide energy so the body functions properly. The amount of calories in a food source depends on the amount of energy the food provides.

Carbohydrates

These nutrients form a major source of energy for our food and provide it with fuel that is required to sustain life; hence we need them in the largest amounts in our diet. Depending on their size, carbohydrates are classified into two basic types, namely, Simple carbohydrates and Complex carbohydrates ; the former are termed as ‘simple carbohydrates’ as they cannot be broken down into simpler sugars while the latter are larger and consist of long strings of simple carbohydrates and hence are called ‘complex carbohydrates’. Examples of simple carbohydrates are glucose & fructose, and those of complex carbohydrates are sucrose, lactose, maltose, starch, fiber etc. Fiber is an indigestible form of carbohydrate. 

Both simple and complex carbohydrates are converted to glucose which can then be utilised by all the cells of the body and the brain as an energy source. Unused glucose is stored as glycogen in the liver and muscles for later use. The glycogen stored in the muscles is used as an energy source by the body during periods of intense physical activity. The brain only uses glucose as an energy source; hence it is imperative to constantly maintain the level of glucose in the blood above the minimum level. When the body uses carbohydrates for energy, it spares the other macronutrients to do other major tasks of tissue growth and repair.

Cereals, fruits, roots are some of the carbohydrate-rich food sources.

Fats

Fats also are energy-yielding nutrients that yield more energy than any other nutrient (9 calories per gram). The extra fat that is consumed is stored in the body in adipose tissues (fat cells) for future use. Fats are classified into ‘Saturated and Unsaturated Fats’.

Besides providing energy, fats have multiple roles to fulfil in our body. Fat-soluble vitamins, such as Vitamin A, D, E, K need fat in the diet for their absorption and transportation. Proper functioning of nerves and brain, maintaining healthy skin and formation of steroid hormones that have a regulatory effect on various physiological processes in the body are few other functions of fat.

Fats are commonly found in oils and animal sources like meat, fish, milk, butter, cheese, ghee etc.

Proteins

Proteins are macronutrients that are formed by combining smaller amino acids, which are the building blocks of life and also contribute to the body’s energy requirement. Some amino acids can be manufactured by our body and need not be included in our diet but certain other amino acids known as essential amino acids, cannot be produced by the body and hence have to be compulsorily included in our diet. All animal foods and plant sources like soy protein and quinoa are good food sources that provide these essential amino acids.

The predominant roles of proteins include growth and repair of body tissues, formation of muscles, hair, nails, skin & organs, production of enzymes, hormones, neurotransmitters & antibodies, and transporting various substances throughout the body.

Animal sources which are rich in proteins are meat, fish, chicken, eggs, milk, cheese and yoghurt and plant protein sources include pulses, lentils, nuts, soy beans, paneer, grains such as quinoa, oats etc.