Malnutrition

The World Health Organization defines malnutrition broadly: it can result from too little, too much or an imbalance of energy and nutrients. Its main forms include undernutrition; micronutrient-related malnutrition, involving deficiencies or excesses of vitamins and minerals; and overweight, obesity and diet-related noncommunicable diseases. These categories can overlap, and a person's nutritional status cannot always be inferred from body size alone.

Several indicators describe undernutrition, especially in children. Wasting means low weight for height and can reflect recent weight loss or failure to gain weight; illness and insufficient food are among its possible contributors. Stunting means low height for age and is associated with prolonged or recurrent nutritional and health challenges. Underweight means low weight for age and may occur with wasting, stunting or both. A shortage of essential vitamins or minerals is another form of undernutrition; such deficiencies may not be apparent from height or weight measurements alone.

Malnutrition has multiple, interacting causes. Dietary quality and quantity matter, but so do food security, disease, access to health services, care practices and the surrounding environment. Poverty and social and economic conditions can influence several of these factors at once. Food insecurity and malnutrition are connected but not identical: inadequate nutrient intake, illness, care and environmental conditions can contribute to malnutrition in different combinations. Undernutrition can increase vulnerability to illness and threaten children's growth and development; overweight and obesity can impair health and raise the risk of diet-related chronic disease.

Assessment depends on the form of malnutrition. For young children, standard measures compare weight with height, height with age, and weight with age; UNICEF and WHO use internationally developed child growth standards for population estimates. Micronutrient status requires other evidence, while adult overweight and obesity are commonly classified using body-mass index alongside clinical context. Because malnutrition has many causes and forms, public-health responses combine nutrition services with measures that support healthy diets, appropriate care, health services and reliable access to food. UNICEF's framework emphasizes diets and care as immediate determinants of maternal and child nutrition, within a wider set of social and environmental influences.