You haven’t traveled anywhere — and yet you’re still experiencing effects akin to jet lag. In this case, it’s not landing in a different time zone that’s to blame but so-called social jet lag. Essentially, your body’s internal clock is out of sync with your constantly shifting sleep schedule.
During the week, people often go to bed relatively late and then get up early for school or work. Then on the weekend, people tend to go to bed even a little later and sleep in the next morning. And our social choices — extending to those we make for work or play, essentially the way we schedule our lives — can have an impact not only temporarily, when you feel groggy or not so ready to take on the day, but in more lasting ways on our waistlines and health in general, research indicates.
“So they have this very irregular sleep pattern, that then when Monday morning rolls around, they start the whole cycle over again,” says Susan Malone, a senior research scientist at the NYU Rory Meyers College of Nursing in New York City. She led research, published in the journal Chronobiology International in 2016, that found social jet lag was associated with higher body mass index, or BMI, in adolescents.
More study is needed to understand the link between social jet lag and obesity in teens and adults, as well as its association with heart disease and diabetes found in other research. But experts say what’s becoming clearer is that sleep regularity — not just sleep duration, or whether a person fails to get sufficient sleep, though the two are commonly connected — can have an impact on health.
One way to conceptualize this is thinking about adolescents staying up late on a Friday night — “almost as if they’re flying to California, in some cases,” Malone says. “Then when Monday comes around they have to get up early — so they’re flying back to the East Coast. So that’s why we call it social jet lag,” she explains. “They’re not actually flying to California and back, but in reality that’s what their bodies are doing in terms of the hours that they’re choosing to stay awake and go to sleep.” And, of course, the same applies to adults.
“A lot of the systems in the body that control metabolism, energy regulation, food cravings, how our body uses energy and how it stores energy and all these sorts of processes are all connected with each other, and those are all connected to rhythms,” says Dr. Michael Grandner, director of the Sleep and Health Research Program at the University of Arizona. When you disrupt these rhythms you throw a wrench into the system, he notes.
Your cells might not work as efficiently at turning food into energy, and lowering blood sugar levels, or you may crave high-calorie foods — like when you’re struggling to stay awake at night and reach for something sweet. How well your immune system functions is also closely tied with sleep. Keeping regular bedtimes and getting enough zzz’s can help your body fight off diseases, while not doing so can leave you more vulnerable to getting sick.
“When you disrupt the ability of the immune system to function, it’ll disrupt how your body manages insulin and glucose and how it processes energy,” Grandner adds.
While some people seem more equipped to burn the candle at both ends than others, in general when we try to ignore our circadian rhythm, and for that matter forgo regular mealtimes or snack times, there can be consequences, experts note. At the very least we’re less efficient.
“Our bodies internally have these clocks that kind of dictate when we should be sleeping, when we should be eating. And they dictate this by sending out these waves of hormones at certain times of the day; and it’s very, very regulated,” Malone explains. So, for example, hours before a person goes to bed, there’s a surge in the release of the hormone melatonin, which rises gradually and peaks overnight to help individuals fall asleep and stay asleep. “So the sleep that you get during the daytime, when you don’t have melatonin in the system, is much less restful and less efficient,” she says. That can make things tough for shift workers, who toil at night and sleep during the day. “Even before this connection with sleep and obesity, (we’ve known) for quite a while that shift workers seemed to be at a greater risk for obesity, diabetes, cardiac disease,” Malone adds.
Like melatonin, levels of insulin — a hormone that regulates glucose, or sugar, in the blood — follow cyclical patterns, which can be disrupted by social jet lag. “Melatonin is high during the night and low during the day. Insulin is just the opposite: It’s high during the day, and low during the night, and we know that we need insulin to process our food well — to get it to the muscles and to the tissues where it needs to go,” Malone says. “If we are engaging in certain behaviors in times that are out of sync with when these hormones are kind of flooding our body, we’re less likely to be able to function as efficiently — like (with) sleep. It’s much harder to sleep during the daytime. If you’re eating during the night or past a certain hour, you’re much more likely to have higher blood sugars that don’t come down.”
[See: How to Optimize Your Metabolism.]
In addition to any disruption of blood sugar regulation, the link between social jet lag and obesity is thought to be another possible reason it’s associated with higher rates of diabetes. Disruptions in sleep and body rhythms may also over time — say, when social jet lag and sleep loss are chronic — affect blood pressure and function of blood vessels, and could have an impact on heart health.
To turn the tide, experts say it’s important to dispense with an anything goes — or when you can get it — approach to sleep, and instead opt for more fixed bedtimes and wake times. “Regularity is important, and the more regularity we can build into the system, the better,” Grandner says. Your sleep schedule doesn’t have to be exactly the same every night. “But the closer you can have to a regular schedule, the happier your body’s going to be,” he says.
Besides the alarm you probably already use to get you up in the morning, try one to remind you when you need to get ready for bed. “Set a bedtime alarm,” Grander suggests. “And try sticking to it. That might help give you a cue of when you need to be starting to wind down.” That’s in addition to other best practices for sleep, like not staring at a screen right before you’re trying to knock off, so that you’re not artificially keeping yourself up.
“One of the things we can do to reduce social jet lag is to try to make sure we’re getting sufficient, adequate sleep every day of the week — not just on the weekend — not just catching up for all the sleep we missed during the week,” Malone adds. Experts stress that it’s a mistake to think you can make up for sleep lost during the week simply by sleeping in on the weekend, and that — as seen with social jet lag research — trying to do so can instead have a harmful effect. Instead you should get seven to nine hours per night, depending on what you require to feel well-rested, awake and alert during the day.
That principle of adhering more closely to a natural schedule applies for other areas of life as well, like when you eat. “The more regular you make your schedule for your body, the happier your body is,” Grandner says. “It likes schedules. It likes rhythms. It likes being able to train itself to a rhythm — and it helps it function more efficiently.”
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