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METABOLIC RESPONSE TO STARVATION

With most insults to the host, metabolic adaptive protective responses are initiated. The protective adaptive metabolic response to starvation is schematically described. This schema is important to understand in order to better understand the contrasting response to a burn.

The key adaptive components are:

An overall decrease in energy needs and caloric requirement to compensate for the lack of nutrients. Calorie requirements decrease to 20-25 kcal/kg/day as does body temperature.

The majority of energy comes from the fat depot in the form of ketones mobilized by a high growth hormone and low insulin level.

Obligate glucose users like brain require glucose production by the liver (gluconeogenesis) from amino acids.

These amino acids mobilized from the lean mass compartment are converted to alanine, then pyruvate, then glucose leading to a modest protein loss. However, the higher growth hormone levels increase the efficiency of protein synthesis such that erosion of lean mass is minimal. The hormone regulated metabolic adaptation is protective.