gardening jobs, can be extremely hazardous if handled by a sleep-restricted user. In my practice I always caution teen patients to stay away from dangerous equipment and to not drive until their sleep debt is paid off. When sleep deprived they just can’t think clearly enough or react fast enough to use machinery safely.

Sleepiness can also increase teens’ risk of sports injuries. Just as they can suffer an attention lapse on the road or while using a power tool, they can tune out for a few seconds and run into another player or get hit by a bat or stick because they’re not attentive to their surroundings. Reduced reaction time can also make it difficult to avoid being hit by a wild pitch or to sidestep an obstacle. And, of course, sleep-deprived players won’t be able to perform anywhere near their best. A recent study of aces and winning serves on a tennis team showed evidence of a strong link between serving aces and having adequate sleep. Another study, led by a researcher at the University of Chicago Medical School, found that after only a week of sleep deprivation, men ages 18 to 27 metabolized glucose (sugar) less efficiently and had elevated levels of cortisol, a stress-related hormone. Glucose is the main source of energy for athletes and elevated cortisol levels have been linked with impaired physical recovery.

Though it may seem counterintuitive, the less you sleep, the more weight you gain. You might think that being awake longer would help you burn more calories, keeping weight from piling on, but in reality not getting enough sleep makes it more likely you’ll become obese. That’s because sleep loss decreases the level of hormones called leptins, which tell the body its full, and increases the level of ghrelin hormones, which trigger the appetite to pick up. When you’re sleep deprived you feel hungry and you can eat more than you should. On the other hand, getting more sleep actually supports metabolism and has a protective effect against obesity.

Studies of overweight and obese patients indicate that they sleep