Deep Sleep May Aid Muscle, Fat Use and Brain Health

Deep sleep helps the body release growth hormone, which supports muscle and bone maintenance, fat use, and blood-sugar regulation. Researchers at the University of California, Berkeley, identified brain cells involved in this process and found that the connection works both ways: sleep prompts hormone release, while the hormone sends signals that help shape the shift toward waking.

The team studied mice in Yang Dan’s laboratory, recording brain activity with implanted electrodes and light-based stimulation. They focused on the hypothalamus, including cells that encourage or restrain growth hormone release. During REM sleep, activity in both cell groups rose together. During non-REM sleep, one group became less active while the other increased moderately, yet both sleep stages supported hormone secretion through different patterns.

The researchers also traced the hormone’s effect on the locus coeruleus, a brainstem region involved in alertness, attention, thinking, and exploration. Rising hormone levels increased activity there, helping regulate the sleep-wake cycle, although excessive activity could instead increase sleepiness. The findings may help explain how disrupted sleep affects metabolism and brain function, and could support future work on treatments for sleep disorders linked with metabolic disease and neurological conditions.