You’re up late one night booking your next vacation, and even though you know the dates and destination, you’re overwhelmed by minor details. Should you get a refundable ticket? Window or aisle seat? Rent a car now or later? When you’re tired, you’re less able to distinguish between important and irrelevant information, such as your seat assignment, according to Sean Drummond, PhD, a sleep researcher at the University of San Diego. The result: Even the simplest decision takes on exaggerated importance. Tired people also take riskier gambles to maximize results (“Maybe if I wait until the last minute, the ticket price will go down”) and have trouble adjusting to changing circumstances (like firming up an itinerary if flying from an unfamiliar airport).

Shortchanging your nightly sleep can make your waistline suffer. Studies show that chronic sleep loss can disrupt blood sugar levels and cause the body to produce less leptin, a hormone that curbs appetite, and more ghrelin, leptin’s hunger-stimulating counterpart. Because of these physiological changes, you may be more likely to overeat when you skimp on sleep—and the food you pick probably won’t be either nutritious or a lasting source of energy. Tired people tend to be particularly drawn to sugars and other simple carbohydrates, probably because the body is looking for a quick pick-me-up, says Lisa Shives, MD, a spokesperson for the American Academy of Sleep Medicine. Sleep deprivation also tends to erode self-control, making you more likely to choose a brownie over carrot sticks.

Inadequate sleep can leave you more vulnerable to infection than those who are well rested. In one study, researchers injected healthy volunteers with a cold virus. Those who slept less than 7 hours a night for the previous week were 3 times more likely to develop symptoms than those who got 8 hours or more. In another study, people who got only 4 hours of sleep for several nights in a row had a weaker immune response to the flu vaccine than those who slept between 7.5 and 8.5 hours

Do those ballads on American Idol move you to tears? Don’t automatically chalk up your sudden weepiness to PMS: Without sleep, you are more emotionally volatile. In one brain-imaging study, for example, people who missed a night of sleep and viewed disturbing images had 60% more activity in the amygdala, which is involved in processing fear and anxiety compared with better-rested volunteers. The study also found that the sleepy volunteers’ amygdalae communicated less with the part of the brain that determines appropriate emotional responses, suggesting that they weren’t doing a good job of tempering their emotions. When we’re sleep deprived, we may also feel gloomy because tired brains store negative memories more effectively than positive or neutral ones. As a result of all this, Shives says, “if you are chronically sleep deprived, you could act like someone with depression."

One moment you’re brewing a cup of afternoon tea and the next thing you know, you’ve spilled it all over your new dress.

Sound familiar? Researchers have accumulated ample evidence that the sleep deprived have slower and less precise motor skills, but exactly why isn’t yet known, says Clete Kushida, MD, PhD, director of Stanford University Center for Human Sleep Research. Sleepy people may be clumsier for several reasons: Impaired reflexes and a lack of focus may make it hard for them to react quickly enough to things that spring up in their path. Another possibility: Sleepiness throws off balance or depth perception. In any case, it’s not uncommon for very sleepy people to black out momentarily when the body’s urge to sleep gets too strong. So it’s possible that your klutziness stems from “microsleeps” that last for a second or two, Kushida says—just long enough to trip on the curb or drop a glass.

I don't know about you but I sure hell need to reset my body clock and stop skimping on my zzzs after I gathered info for this blog post. We all know how lack of sleep can be unhealthy, we just didn't know until now how disastrous it can go.