According to the WHO, “Nutrition is a critical part of health and development. Better nutrition is related to improved infant, child and maternal health, stronger immune systems, safer pregnancy and childbirth, lower risk of non-communicable diseases (such as diabetes and cardiovascular disease), and longevity. Malnutrition, in every form, presents significant threats to human health. Today the world faces a double burden of malnutrition that includes both under-nutrition and overweight, especially in low- and middle-income countries”. These statements by the WHO emphasize not only the importance of nutrition for humankind but also the significance of undernutrition, over nutrition and malnutrition. All these nutritional disorders have been thoroughly covered in this chapter of Practice of Medicine called Nutritional Disorders.