Marasmus is a type of malnutrition which is caused by calories deficiency, which means it occurs when there is not enough intake of either fat or carbohydrates. Animal food (milk cream, cheese, meat, pork, etc) and nuts are rich in saturated fat and unsaturated fat (oil), which have been vital for brain growth and development during human evolution, while plant food, such as wheat, corn, rice, and fruits contain carbohydrates in the form of starch and sugar. Both fat and carbohydrates have calories, which are vital for cell metabolism. The lack of calories can cause growth and mental retardation.
As a result of marasmus, there is subcutaneous fat and muscle mass loss due to liver cannibalism. This organ, in order to offset the lack of calories intake, begins to break down the body muscle in order to produce and supply calories to the body tissues. Because the body cells need calories, they absorb the available energy stored in the body in the form of fat (lipid), but once we run out of body fat (when we do not have more fat to burn), it then that the liver begins to dissolve our skeletal muscles to make calories.
Marasmus as well as Kwashiorkor are very common in poor countries, such as Somalia, Sudan, and Ethiopia, where there is food shortages, and is usually accompanied by kwashiorkor, which is protein deficiency.