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Sleepiness makes fatty foods extra tempting

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Sleepyheads, please refrain from licking your monitor.

Slacking off on shuteye could make it harder for you to resist high-calorie treats and fattening foods, new research found.

Feeling drowsier during the day because you didn't catch enough ZZZs at night may make it easier for you to give in to temptation, suggests a preliminary study to be presented at the 2011 meeting of the Associated Professional Sleep Societies.

In this small study of 12 healthy adults, ages 19 to 45, participants were shown photographs of low- or high-calorie foods over a four-minute period as images of their brains were scanned. Volunteers were told they would be given a memory test afterward to make them focus on the visuals.

Every few seconds new images would flash before participant's eyes including such healthy fare as salads, fresh fish, an apple or orange. They also saw more enticing edibles from strawberry cheesecake and french fries to cheeseburgers and chocolate cake. As a control, researchers sprinkled in shots of trees, rocks, and flowers.

Volunteers also completed questionnaires about how drowsy they were during the day as well as their food likes and dislikes and typical eating habits.

Scientists found that "the sleepier you are, the less the prefrontal cortex -- the inhibitory area of the brain -- is activated when it's shown high-calorie foods," says William Killgore, an assistant professor of psychology at Harvard Medical School and McLean Hospital in Belmont, Mass.

In other words, if you've skimped on sleep, you're less likely to put on the brakes when you're around fattening foods. And you're more likely to reach out and grab that bacon double cheeseburger or dig into a pint of Chunky Monkey.

In the research, participants were not chronically sleep-deprived. They had the usual tiredness that comes from staying up past their bedtime by an hour or two a night. Even this was strongly correlated with less activation in the inhibitory areas of the brain when shown calorie-rich foods.

When you don't get the rest you need, "you might not have the ability to say no to that extra cookie or dessert," points out Killgore, and you're a little more likely to take in a few extra calories a day.

"Even subtle changes in sleep could be having larger effects in ways we hadn't considered, such as appetite, body weight, and food choices," explains Killgore. A little bit of sleep loss adds up and may influence your body shape. 

"It's entirely plausible that with less inhibitory control, you reach for less optimal foods, and this may lead to a lot more weight over a lifetime," Killgore says.

And a fatigue-induced lack of inhibition can extend to behaviors beside eating. Other studies have suggested that being sleep deprived affects a person's ability to plan and think ahead, and skews judgment when assessing risk.

When you're tired during the day, are you more likely to go for junk food?