If you haven’t gotten enough rest the night before, the telltale sign could sit right on top of your nose. Acne can flare up when you aren’t getting enough sleep. In fact, sleep deprivation is considered one of the three main acne triggers, along with stress and sweating. Studies have borne this out. It’s possible that by disrupting your hormones, sleeplessness also unsettles the chemical balance in your skin that wards off pimples.

Sleeplessness takes its toll on your face. Researchers have found that your mouth, forehead, and eyes can reveal to others that you aren’t getting enough rest. In particular, one of the hallmark signs of sleepiness is the presence of dark circles and puffy eyes.

Not all dark circles come from sleep loss, but it is often a contributing factor. One study looked at 200 subjects, mostly women, who had periorbital hyperpigmentation—the medical term for dark circles around their eyes. Of these subjects, 40% suffered from lack of adequate sleep, including insomnia.

In another research test, observers were asked to rate the faces of subjects. A photo of each subject was taken after a full night’s sleep, and another was taken after only 5 hours of sleep, followed by 31 hours of wakefulness. Observers identified the well-rested faces as being more alert, youthful, and attractive most of the time. They also noted eye puffiness and dark circles as one of the most obvious signs the subjects didn’t get enough sleep. Not only that, but the observers judged faces with little rest as appearing sadder as well. So if you want to give off a cheerful vibe, make sure you’re in bed at bedtime.

If you’ve had trouble sleeping recently, don’t be surprised if you gain a few extra pounds. Less than six hours of sleep per night puts you at an increased risk of obesity. To understand why, you need to know how sleeplessness affects your body.

When you lose sleep, your body chemistry changes. The hormones that control hunger become imbalanced, leading you to feel hungry more often. You also become less sensitive to insulin, the chemical that lets you absorb the energy from sugar.

The results of these changes have been shown in the laboratory. People forced to go without sleep eat more—particularly high-carb snacks. Those results were confirmed in at least two studies. So if you aren’t getting enough time in bed, watch out for the munchies. They seem to be harder to control when you go without sleep.

Salty and sugary snacks are especially hard to avoid when you don’t get enough zzzs. Your body seems to crave higher-calorie foods when you’re tired. Given that many calorie-packed foods are sweet or salty, this connection makes sense.

Aside from the obesity risks discussed earlier, eating too much salt and added sugar has been associated with serious health problems. Getting too much sugar puts you at greater risk of diabetes and heart disease, among other conditions. Too much salt can damage your heart and kidneys, and may also harm your bones.