Stop and Think Thursday

The body fasts during sleep. In non-carnivores, the liver maintains a steady glucose supply using stored glycogen. In carnivores, or people on a very low-carb diet, liver glycogen stores are lower, so the body primarily uses gluconeogenesis (creating glucose from non-carbohydrate sources like amino acids from protein) to fuel the brain.
The brain is highly sensitive to low glucose and triggers an alarm system to ensure it gets the necessary fuel.
Sympathetic Nervous System Activation: This alarm involves the activation of the sympathetic nervous system (the "fight-or-flight" response).

Hormone Release: In response to the perceived energy crisis, the adrenal glands release stress hormones, primarily adrenaline (epinephrine) and cortisol.

Physiological Awakening: These hormones work to raise blood sugar by stimulating the liver to produce and release more glucose. The surge of adrenaline and cortisol also increases alertness and heart rate, which physically wakes the individual from sleep and makes it difficult to fall back asleep.