Marasmus refers to malnutrition caused primarily by severe reduction in caloric intake.

It results in greater than 60% reduction in body weight adjusted for height and sex.

A child with marasmus suffers growth retardation and loss of muscle. The loss of muscle mass results from catabolism and depletion of the somatic protein compartment.

This seems to be an adaptational response that serves to provide the body with amino acids as a source of energy.

Interestingly, the visceral protein compartment, which is presumably more precious and critical for survival, is depleted only marginally, and hence serum albumin levels are either normal or only slightly reduced. In addition to muscle proteins, subcutaneous fat is also mobilized and used as a fuel.

With such losses of muscle and subcutaneous fat, the extremities are emaciated; by comparison, the head appears too large for the body. Anemia and manifestations of multivitamin deficiencies are present, and there is evidence of immune deficiency, particularly of T cell-mediated immunity.

Hence, concurrent infections are usually present, and they impose an additional stress on an already weakened body.

Marasmus and kwashiorkor are two ends of a specimen and considerable overlap exists.