Protein-energy malnutrition (PEM) is a severe nutritional disorder characterised by a deficiency in both calories (energy) and protein intake. It results in inadequate nourishment, leading to muscle wasting, stunted growth, weakened immune function, and other health complications. PEM can manifest in various forms, including marasmus and kwashiorkor.

Food is any substance consumed by living organisms to provide essential nutrients and energy for growth, maintenance, and the sustenance of life. Food provides our bodies with the necessary nutrients, such as carbohydrates, proteins, fats, vitamins, and minerals, which are the building blocks for various bodily functions. These nutrients supply energy for physical activities, support growth, and help repair and maintain our tissues. Food also serves as a source of essential amino acids and fatty acids that our bodies cannot produce on their own.

Nutrients are the substances found in food that are needed for biological activity and are essential to health and life. There are five types of substances that we have categorised under nutrients; such nutrients are carbohydrate, protein, fat, vitamins, and minerals. Carbohydrates and fats provide energy to our bodies. Proteins help in repairing and building body tissues. Vitamins and minerals help in healing wounds, boosting immunity, etc.