There's very few of us out there that would refuse an extra hour's sleep when offered to us.
Who wouldn't want an extra hour or two in the place we're at our most comfortable? Of course lie ins do have their drawbacks. The grogginess and general disorientation when you immediately wake up and the general feeling of being tired throughout the day afterwards. But why are we feeling this way? We slept longer than usual. Shouldn't we feel better rested?
Well, no, actually. Not according to the science involved.
When you wake up at the same time every day, say 6am, for work.
Your brain develops a sleep-wake schedule. It prompts your body to rise by releasing higher levels of hormones like dopamine and by increasing your body temperature so that you'll feel alert, energized and rested when that time comes around.
However when you choose not to rise at the usual time and decide to lie in for an extra few hours, your brain gets confused and doesn't know when to prepare your body to wake up. So you might end up waking up in the middle of your deep sleep—or REM sleep—cycle.
Dr. Chris Winter says “It becomes kind of like jet lag. You wake up feeling kind of groggy, like you have a dull headache, maybe a bit of nausea, and lethargy—you just don’t feel like doing anything.”
The best thing you can do is resist the urge to nod back off to sleep after your first wake up. However if you really decide you need five more minutes there is a compromise.You can take an extra twenty minute snooze, but no more than that. If you only sleep for that much longer you're unlikely to fall back into a deep sleep and will avoid the symptoms mentioned above when you get out of bed.
If you do end up sleeping in for too long and need relief from the awfulness as soon as possible, the best thing to do is to get out of your dark room and get all the lights on straight away. Bright lights tend to prod your body into wakefulness.
Via Men's Health