To protect vital protein stores, the body "spares" glucose in the post-absorptive state by inducing most tissues to switch from glucose to fatty acid and ketone utilization. 

During the absorptive state, glucose is "spared" by converting it into urea, which can be stored in the liver for energy during chronic starvation.

The body "spares" glucose by increasing the theoretical maximum yield of ATP from glycolysis, allowing cells to survive on less fuel during the post-absorptive state.

"Glucose sparing" is a metabolic adjustment that occurs during the fed state to ensure that excess dietary glucose is delivered exclusively to the adipose tissues.