A severe form of malnutrition caused by overall deficiency of energy and protein, producing extreme wasting in young children. Affected children appear skeletal, with loss of muscle and fat, an old-man face, and apathy, but typically without the oedema seen in kwashiorkor. Marasmus results from inadequate food intake, whether from famine, poverty, or diseases that prevent nutrient absorption. Also described as failure to thrive in clinical contexts, it impairs growth, immunity, and brain development. Treatment uses phased therapeutic feeding with specialised milk formulas, alongside treatment of infections. Long-term recovery requires sustained access to adequate, nutritious food and health care.