There's a big downside to sleeping in on a Saturday.
If you normally sleep, say, 11 pm to 7 am on weekdays but 1 am to 11 am on weekends, you're essentially putting your brain through jetlag. It's the equivalent of shuttling back and forth between New York and California. And it's one reason why so many people end up feeling terrible on Monday mornings.
Sleep researchers refer to this phenomenon as "social jetlag" — when work, school, or social obligations force your body away from its normal sleep patterns. Not only can it explain why so many people feel awful on Monday mornings, but social jetlag seems to also have real health consequences.
Recently, researchers have been discovering that when you sleep can be as important as how much you sleep. Even if you get your recommended eight hours a night, you can still feel terrible if you are going to sleep and waking up at different times over the course of a week.
Everyone is wired to sleep at very specific times
There are a few things that determine when your body should go to sleep. One is exposure to light, which reduces your body's production of melatonin (the hormone that makes you sleepy).
But the other major factor is determined by your own particular biology. Some people are naturally early risers, and some people are night owls, preferring to wake up later. Neuroscientists have actually studied and documented the differences between these types. Unfortunately, you can't really choose to be one or the other — your body chooses this.
To make things even more complicated, preferences for sleep times can vary over a lifetime. For example, many young children are naturally early risers. Teenagers are naturally later risers. And adults can easily be early birds or night owls. You probably have a good idea of which one you are.
But social norms often clash with your body's sleep needs
Of course, not everyone gets to go to sleep and wake up whenever their body tells them to. Night owls often have to get up early to go to work. And early risers often have to stay up at night if they want to hang out with their night-owl friends.
And that can create real problems. Not only is being groggy on Monday mornings a pain, but researchers are beginning to compile evidence that shifts in when people sleep affects their overall health.
The most extreme example of this is with shift workers. Researchers have found that people who work at night are at higher risk for diabetes, heart problems, and possibly even cancer.
But these people aren't the only ones at risk. Over the past few years, some research has been indicating that even a modest variation in waking and sleeping times can create health issues.
In 2012, German research Till Roenneberg co-authored a study in Current Biology finding that even the normal social jetlag that occurs between weekdays and weekends was correlated with increased body-mass index for overweight people. A lag of just one hour increases the likelihood of obesity by about a third. (This was based on a huge internet survey of 65,000 Europeans.)
People who are naturally night owls seem to be particularly affected, perhaps because their natural needs are so at odds with our 9-to-5 workdays, which is geared toward early risers' needs. A few studies have found that night owls are more prone to depression and that obese night owls are more likely to have sleep apnea.
Of course, these are correlational studies, and they don't prove that social jetlag is necessarily causing all these problems. However, other evidence from sleep experiments in people and animals suggests that links between sleep schedule, metabolism, and health problems are quite plausible.
How to defeat social jetlag and feel OK on Mondays
1) Get more sleep during the week. If you're under-sleeping during the week, you're probably trying to catch up on weekends. But that catch-up sleeping-in on weekends just sets you up for terrible Monday mornings.
2) Wake up earlier on the weekends. It sounds painful, but try it out for a weekend, and see how you do on Monday. (If you combine #1 and #2, you can think of it as essentially shifting sleep from one time in your week to another. You don't actually have to lose any of your precious time doing this.)
3) Take smart weekend naps. If you find you need a nap on Saturday or Sunday, do it between noon and 4 pm for 30 minutes or less, which will be less likely to interfere with your sleep at night. That's according to Bernie Miller, supervisor at the Sleep Disorders Center at Mayo Clinic in Arizona, via Popular Science.
4) Get sunlight on Monday. If you are tired on Monday morning, get outside and get some sunlight. Remember, your circadian rhythm is set by your eyes' exposure to light, which directly sends signals to your brain to wake up. Even a cloudy day outdoors can be several times brighter than the average office space (which is often on the darker side to accommodate computer screens).
5) If all else fails, get some blue light. If you absolutely can't get outside or you have been plagued with a work schedule that requires you to get up before the sun rises, then crank up those lightbulbs indoors. Because the circadian rhythm is specifically responsive to blue light, you also might consider getting a lamp or lightbulb that shines blue-ish light. Several companies sell special lighting apparati for just these kinds of purposes.