Malnutrition refers to a condition that occurs when a person's diet does not provide the proper balance of nutrients, or when the body is unable to properly absorb or use those nutrients. This can result in either deficiencies or excesses of specific nutrients, leading to a wide range of health problems. Malnutrition includes both undernutrition (lack of essential nutrients) and overnutrition (excessive intake of certain nutrients or energy, such as calories and fats).