Scientists discover sleep switch that builds muscle, burns fat, and boosts brainpower (opens in new tab)

Deep sleep does far more than rest the body — it activates a powerful brain-driven system that controls growth hormone, fueling muscle and bone strength, metabolism, and even mental performance. Scientists have now mapped the neural circuits behind this process, uncovering a delicate feedback loop in which sleep boosts growth hormone, and that same hormone helps regulate wakefulness.