FAT. Research shows that people who get fewer than seven hours of sleep a night are 30 percent more likely to be obese. Lack of sleep alters the flow of hormones that regulate hunger and satiety, which can cause you to eat more. And when you're sleepy, you're more likely to reach for high-fat, high-calorie foods to keep you going, says Jodi A. Mindell, Ph.D., author of Sleep Deprived No More.
PRONE TO HEART DISEASE. Women who regularly get fewer than five hours of sleep per night are significantly more likely to suffer from hypertension -- a leading heart disease risk factor, according to a recent study. When you're sleep-deprived, your body produces more stress hormones and other substances that increase inflammation, which can up your risk of heart disease and stroke
DEVELOP DIABETES. Those who get fewer than five hours of sleep per night have two-and-a-half times the risk of getting diabetes compared with those who snooze for seven to eight hours, according to a study published in the Archives of Internal Medicine. The likely reason? Suppression of deep sleep, the most restorative sleep stage, significantly decreases your ability to regulate blood-sugar levels, according to new research.
CRANKY. Scientists have found that sleep deprivation makes the amygdala (the part of your brain that processes emotional events) go into overdrive and the prefrontal cortex (the part of your brain that regulates reasoning) become deactivated, making you feel less stable than usual. Lack of sleep makes the brain unable to put emotional experiences into context and produce rational responses, says researcher Matthew Walker, Ph.D.
SICK MORE OFTEN. While you're asleep, your body produces cytokines, chemicals that help the immune system fight off infection and disease. "Sleep not only affects how well your body fights infections but also determines how well your body produces antibodies after a vaccination," says Mindell. "Research shows that people who lack sleep produce half as many flu antibodies after receiving the flu vaccine."