Protein-energy malnutrition is a basic lack of food (from famine) and a major cause of infant mortality and morbidity worldwide.
Starvation is called protein-energy malnutrition because the two most essential things food provides are protein and energy. When primarily a lack of protein in the food, the illness caused in children is called kwashiorkor. When the food supply does not provide enough energy (calories), the illness caused is called marasmus.
In marasmus there is extreme thinness (wasting), especially of the arms. In kwashiorkor you don't look so thin, partly because the body retains more fluid, but you stop growing (stunting).
Both can occur together. In both you often have a swollen tummy (distended abdomen due to fluid or gases), reduced resistance to infection, impaired learning ability (mental retardation) and are short (stunted growth). This can limit both physical and mental ability to perform many activities.
Adults are also severely affected in famines by protein-energy malnutrition, but the children usually start dying first.
Protein-energy malnutrition caused 0.46% of all deaths worldwide in 2002, an average of 42 deaths per million people per year.