Dr. Gregory Carter, a sleep medicine specialist at the University of Texas Southwestern Medical Center in Dallas, said the daily, or circadian, cycles guide the body's internal clock.
People can delay their circadian clock by up to 1 hour by sleeping in 1 hour or more over the weekend, but the problem is that after sleeping in on weekends, the brain's circadian clock can be delayed up to 2 hours, making it tough to get to sleep Sunday and even more difficult to wake Monday morning.
Carter said turning in earlier was more effective than sleeping in later.
"To maintain our internal clock, we need to go to bed 8 hours before our usual time for getting out of bed in the morning," Carter said in a statement. "Too many of us 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 emails just prior to bedtime -- makes for a painful Monday wake-up call."