Marasmus is a severe form of protein-energy malnutrition that results from inadequate calorie and protein intake, most commonly seen in young children in developing countries. It is characterized by extreme wasting of the body due to loss of fat, muscle, and other tissues. Key causes include poverty, inappropriate infant feeding practices, infections, and lack of access to sufficient nutritious foods. Treatment focuses on gradually refeeding the individual with a calorie- and protein-rich diet along with managing medical complications. Preventive measures center on promoting proper infant and young child feeding, improving family access to food, and increasing community nutrition education and hygiene practices.