A neuroscientist explains the biology of sleep and dreaming, and argues that chronic sleep loss drives disease, obesity, and cognitive decline in modern society.
If you cut calories but don't sleep enough, most of the weight you lose comes from muscle and other lean tissue, not fat. Sleep decides what the body gives up when food runs short, so dieting while sleep-deprived largely defeats its own purpose.
Sleeping six hours a night for ten days raises brief involuntary lapses of attention as much as missing a whole night of sleep does, roughly fourfold. Chronic small shortfalls add up to serious impairment, and a night without sleep impairs you about as much as being legally drunk.
Too little sleep raises the hormone that makes you feel hungry and lowers the one that tells you you've had enough. So you keep wanting to eat even when you're full, and short sleepers eat more and gain weight.
Sleeping pills and similar aids help you lose consciousness without producing true sleep, and they can limit the brain's ability to reach it. They give little help falling asleep and may shorten life, leaving nights worse rather than better.
Sleep is not a passive pause but a busy state that does many separate jobs for both brain and body. It should count as a third pillar of health next to food and exercise, and arguably the base the other two rest on.