It's no secret: We are what we eat. And turns out, we might sleep how we eat, too.

A new study from the University of Pennsylvania's Perelman School of Medicine shows an association between what we eat and how we sleep. The research is published in the journal Appetite.

"In general, we know that those who report between [seven to eight] hours of sleep each night are most likely to experience better overall health and well being, so we simply asked the question, 'Are there differences in the diet of those who report shorter sleep, longer sleep, or standard sleep patterns?'" study researcher Michael A. Grandner, Ph.D., of the Center for Sleep and Circadian Neurobiology at the university, said in a statement.

Researchers examined the daily calories and foods consumed -- down to a glass of water -- by people who were part of the 2007-2009 National Health and Nutrition Examination Survey. They also gathered information on the amount of time the study participants slept, putting them into four categories: "very short" sleepers, who slept fewer than five hours a night; "short" sleepers, who slept five to six hours a night; "standard" sleepers, who slept seven to eight hours a night; and "long" sleepers, who slept nine or more hours a night.

And researchers did, in fact, find an association between the number of calories consumed and how long the study participants slept. Those who consumed the most were more likely to be "short" sleepers. Interestingly enough, "normal" sleepers were the next type to consume a lot of calories, followed by "very short" sleepers and then "long" sleepers, researchers found.

The researchers also identified different associations between sleep time and the types of nutrients the participants ate. For example, very short sleepers consumed less tap water, total carbohydrates and a compound found in red and orange foods, compared with the other kinds of sleepers. Meanwhile, the long sleepers consumed less of a compound found in tea and chocolate, as well as the nutrient choline (in eggs and some meats) than other kinds of sleepers, but more alcohol.

Overall, researchers noted that the very short, short and long sleepers consumed a less varietal diet than those who were considered normal sleepers. The question is now whether changing eating habits can actually affect sleep, as the study only showed an association.

"This will be an important area to explore going forward as we know that short sleep duration is associated with weight gain and obesity, diabetes, and cardiovascular disease," Grandner said in the statement. "Likewise, we know that people who sleep too long also experience negative health consequences. If we can pinpoint the ideal mix of nutrients and calories to promote healthy sleep, the healthcare community has the potential to make a major dent in obesity and other cardiometabolic risk factors."

It's important to note that this study only showed an association and doesn't prove that eating certain foods caused a person to have short sleep, or vice versa -- that having short sleep causes a person to eat certain foods or consume certain nutrients. But still, the findings are interesting because recent research has revealed just how big of an interplay sleep and weight have -- particularly in influencing risk for obesity.

For example, a recent commentary published in the Canadian Medical Association Journal showed that "an accumulating body of evidence suggests that sleeping habits should not be overlooked when prescribing a weight-reduction program to a patient with obesity."

And in another study, conducted also by Grandner and presented at a meeting of the American Academy of Sleep Medicine and Sleep Research Society, researchers showed that not getting enough sleep can actually affect how hard it is to say 'no' to unhealthy foods, HuffPost's Catherine Pearson reported.

For more on how what we eat affects how we sleep, click over to blogger Dr. Michael Breus's posts here and here.

Also on HuffPost:

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  • You're Ravenous

    If you find yourself hungry all day (and not because you skipped breakfast or have recently amped up your gym routine) it might be because you've been skimping on sleep. Research presented at the 2010 meeting of the Society for the Study of Ingestive Behavior linked little shuteye with <a href="">higher levels of the hormone ghrelin</a>, the same one that triggers hunger, HuffPost reported. This uptick in the hunger hormone seems to lead to not only increased snacking, but also a hankering for <a href="">high-carb, high-calorie foods</a>, according to a 2004 study, which may help explain why people who don't get enough sleep are at a greater risk of obesity.

  • You're Weepy

    Ever find yourself tearing up over an embarrassing TV commercial? While women might be quick to blame PMS, it could be a lack of sleep sending your emotions into overdrive. A 2007 study found that sleep-deprived brains were <a href="">60 percent more reactive</a> to negative and disturbing images, <em>USA Today</em> reported. "It's almost as though, without sleep, the brain had reverted back to more primitive patterns of activity, in that it was <a href="">unable to put emotional experiences into context</a> and produce controlled, appropriate responses," Matthew Walker, senior author of the study, said in a statement.

  • You're Forgetful Or Unfocused

    You might be tempted to blame your trouble focusing on your age or stress or your overflowing email inbox, but a lack of sleep could be the true culprit. Too few hours in dreamland has been linked to a <a href="">whole host of cognitive problems</a>, like difficulty focusing and paying attention, confusion, lower alertness and concentration, forgetfulness and trouble learning, WebMD reports. So next time you find yourself forgetting where you put your keys, consider how much sleep you got last night.

  • You Can't Shake That Cold

    If you keep coming down with the sniffles -- or can't seem to kick that never-ending case -- you might want to assess your sleep schedule. A 2009 study found that people who sleep fewer than seven hours each night have almost <a href="">three times the risk of catching a cold</a> than people who slept for at least eight hours, the <em>LA Times</em> reported.

  • You're Clumsier Than Usual

    First you knock the alarm clock off the dresser, then you spill the milk as you're pouring your cereal, then you stub your toe on the way out the door -- you've become a klutz overnight. Researchers don't know exactly why, but sleepy people seem to <a href="">"have slower and less precise motor skills,"</a> Clete Kushida, M.D., Ph.D., director of Stanford University Center for Human Sleep Research told <em>Prevention</em>. Reflexes are dulled, balance and depth perception can be a little wonky and since you may also have trouble focusing, reaction time can be slowed, meaning you can't quite catch the egg carton before it hits the floor.

  • You've Lost That Lovin' Feeling

    If you or your partner just can't get in the mood, and stress or an underlying health problem isn't to blame, you might want to spend some extra time between the sheets -- sleeping. Both men and women who don't get their 40 winks experience a <a href="">decreased sex drive</a> and less interest in doing the deed, WebMD reports. A lack of sleep can also <a href="">elevate levels of cortisol</a>, the stress hormone, according to Everyday Health, which doesn't help in the bedroom either.