Protein-calorie malnutrition

Protein-calorie malnutrition is what happens when the body doesn't get enough energy, which comes from calories, or enough protein, or is missing essential amino acids, the building blocks of protein that the body can't make on its own. When it is severe, it shows up mainly in two forms that have their own names: marasmus and kwashiorkor.

In marasmus, what is missing is energy overall. To get energy, the body starts using up what it had stored: its fat and its protein. It's like a piggy bank that you take money out of every day and never put anything back into, until the fat and muscle reserves run out.

In kwashiorkor, what is mainly missing is protein, even though calories are enough or nearly enough. Here what you see is bilateral edema, meaning swelling on both sides of the body. The key is albumin, a protein in the blood that helps keep fluid inside the blood vessels. When albumin drops very low, it becomes hard to hold that fluid in, so it leaks into the tissues and the body swells.