There are lots of sleepless people out there right now. Many of us do not sleep the entire night. Innumerable reasons wake us up – everything from election nights, World Series games, working shifts and tweets from long forgotten lovers, to tobacco (smokers perpetually wake up in nicotine withdrawal) to drinking an alcohol nightcap, depression and anxiety. But if we get less than our presently suggested seven hours of slumber, what happens to us besides feeling cranky, tired and unproductive come morning?
We get hungry.
There are many effects of partial sleep deprivation – and even shift workers often get some sleep during the night (though they are frequently unaware. Sleep is stealthy.) Most of us overcome bad nights with naps and greater sleep periods in subsequent days. But lots of us get the munchies.
And now we’re getting an idea of just how ravenous we get.
The Tale of the Tape
Recently a group from King’s College in London and the Free University in Amsterdam decided to try a sleep-hunger meta-analysis. They looked at the many studies where people were allowed to sleep only four hours, and then how hungry they got the next day.
The average increase in food intake – a hefty 385 calories.
That’s a lot. Extend that across a population of billions of gamers, messagers, parents with infants, emergency workers, night-time cooks and businesspeople connected to global supply chains, and you get one weighty reason for increasing obesity statistics. And what’s curious is what sleepy people eat. In this recent meta-analysis, it’s fat. In other studies, people crave sugar.
Not necessarily the healthiest foods. About a quarter of American workers officially do shift work. Many more do so unofficially, when they hear the pinging of a message from their boss at 3 AM.
As they wake up, many notice something odd – they want to eat. At 3 or 4 in the morning. Some wait for breakfast, but many do not.
So what do you eat at four in the morning? A large salad? Carefully cooked oatmeal?
The general tendency is to grab for high calorie foods and snacks, like M&Ms or “protein” bars. They’re quick, they’re easy. And if you’re a shift worker pounding the hospital wards in the middle of the night, junk food will usually be the only available nutritional delight. As the authors point out, lots of people eat “as a reward.” For many, the perils of a long, relatively sleepless night should be rewarded by a candy bar.
But what is actually happening inside the information system of the human body?
Glucose and Sleep
A group led by Eve van Cauter at the University of Chicago has almost gleefully documented the endocrine results of sleeping less than you want. Their studies find flips in hormones like ghrelin and leptin – a sort of yin-yang pair influencing when we feel hungry or sated. More prominently, they discover that folks who get four hours of sleep, when they’re used to getting seven or eight, suddenly look pre-diabetic. They metabolize glucose rather badly.
And yes, they like to eat a lot more. In the Chicago group’s findings, it’s usually sugary and fatty stuff.
Looking pre-diabetic after one night of just a few hours of sleep deprivation is a potent reminder of all that sleep does. One frequent side result of sleep deprivation is a little bit of hypoglycemia – insulin overshoots where glucose goes so low people feel nauseous, nervous, weak and tired. And, when the body recognizes that glucose is low, it gets hungry.
For though the brain is rather active at night, unlike most of the body it can’t use fat. Brains run exclusively on glucose, as do red blood cells, until long periods of real starvation set in. Meanwhile, glucose stores are drawn down so aggressively during the night that we’re usually digesting our hard won voluntary muscles to make the sugar we need to get through the early morning.
Sleep less, weigh more. All it takes is an early plane ride, an unexpected phone call from a friend who doesn’t realize you’re no longer in the same time zone, an irritable child, or just worry about the state of the nation. That night or the next morning you may find yourself ravenous.
So along with survival, prevention of heart disease, stroke and cancer, improved mood and performance, staying svelte is another reason to protect your sleep every night you can. And if you do find yourself really, really hungry, consider that fibrous foods may staunch that need for calories more effectively than a candy bar. Walking after any meal will also change your metabolism in ways that makes it less likely the extra calories will end up lining your stomach and tightening your waist band.
Sleep is a weighty matter.