Malnutrition is defined as an imbalance between the body's nutritional needs and intake that can lead to deficiencies. It causes symptoms like reduced appetite, fatigue, weakness, and increased susceptibility to illness. Specific diseases related to malnutrition include kwashiorkor, marasmus, anemia, and mumps. Treatment involves addressing the underlying condition, supplements to improve nutrition, and eating a varied, nutritious diet with fruits, vegetables, grains, proteins, and fortified foods. Malnutrition is often caused by poverty, lack of healthcare access, ignorance, weak public support systems, and poor sanitation practices in rural areas.