Enjoying extra hours of sleep during the weekend actually makes you sleepier during the week, according to new research.

Contrary to popular belief, sleeping in on the weekends does not help catch up on sleep lost during the week, and actually makes people even sleepier on Monday morning. Scientist say that the extra hours of sleep on Saturday or Sunday disrupts the body's internal clock so much that it can be more difficult to wake up for work on the weekdays.

"A great myth of sleep deprivation is that if we miss sleep over the course of the work week, we need to catch up on an hour-by-hour basis on the weekend," said lead author Dr. Gregory Carter, a sleep medicine specialist at UT Southwestern Medical Center, according to Health News Digest.

Experts say that the daily or circadian, cycles guide our body's internal clock, and that people can delay their circadian clock, up to one hour, if they sleep an hour or more over the weekend.

They explain that the problem with sleeping in on weekends is that the brain's circadian clock can be delayed up to two hours, which makes it hard to fall asleep Sunday night and even more difficult to wake up Monday morning. Carter recommends going to sleep earlier rather than sleeping in later to balance any "sleep debt" from weekdays. He said that any sleep debt can be compensated by spending eight hours in bed.

Experts say that when people are really sleepy, their brains rest more efficiently. "To maintain our internal clock, we need to go to bed eight hours before our usual time for getting out of bed in the morning," Carter said.

"Too many of us, however, stay up later on Friday and Saturday nights and choose to sleep in on Saturday and Sunday mornings. This pattern - combined with sleep-defeating actions that may include alcohol consumption and late-night checking of e-mails just prior to bedtime - makes for a painful Monday wake-up call," he concluded.

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