Is that 6 a.m. workout getting in the way of good sleep? Don't think your fat cells won't notice.
A new study published in the Annals of Internal Medicine finds that inadequate shut-eye has a harmful response on fat cells, reducing their ability to respond to insulin by about 30 percent. Over the long-term, this decreased response could set the stage for Type 2 diabetes, fatty liver disease and weight gain.
The study adds to a growing body of evidence that there's "an intimate relationship between the amount of sleep we get and our ability to maintain a good, healthy body weight," says sleep expert Helene Emsellem, director of the Center for Sleep and Wake Disorders in Chevy Chase, Md.
But Americans don't seem to be getting the message that we need seven to nine hours per night. More than 1 in 5 of us, according to a report from the Centers for Disease Control and Prevention, is getting six or fewer hours of sleep per night, on average.
So how did researchers study fat cells in the Annals paper? Matthew Brady of the University of Chicago and a group of colleagues recruited seven volunteers — all young, lean and healthy — who agreed to sleep for eight nights in a sleep lab.
"For four nights they were allowed to stay in bed for 8.5 hours a night," says Brady. Then, a month later, they came back for four additional nights — but this time they were allowed just 4.5 hours of sleep per night. And after each visit, researchers got a sample of their fat.
Brady explains that the fat cells responded significantly to the loss of sleep. "I was very surprised to be honest," he says.
Bad things can happen when fat cells become less responsive to insulin. "Fat cells are actually your friend," he says. "They're there to store lipids."
When lipids stay inside the cells, your body can utilize the fat when you're exercising or sleeping or going about your day. "However when fat cells start to become insulin resistant, the lipids start to leach out of the fat cells and rise in the circulation," Brady says.
Once fat starts to accumulate in other tissues in the body such as in the liver, it can lead to fatty liver disease or it can interfere with the body's ability to clear glucose (sugar) from the blood into the muscle. This is what sets the stage for the metabolic problems.
The fat cells of the healthy young volunteers likely rebounded after returning to their normal sleep patterns. But over a lifetime, this new body of evidence challenges the assumption that we can control our weight solely by watching how much food we take in.
"What the message is in this article is that your body may decide to store more of the food [you eat] as fat if you haven't gotten enough sleep," Emsellem says.
If you short yourself just a half-hour a night, the sleep deficit can really accumulate. "Even tiny changes will have dramatic effects" on our bodies, says Francesco Cappuccio of the University of Warwick in the U.K.
RENEE MONTAGNE, HOST:
If you're not getting enough sleep each night, your fat cells may be taking notice and not in a good way. As NPR's Allison Aubrey reports, a new study finds that sleep deprivation seems to have a direct effect on our fat cells. And in the long term, that may lead to problems.
ALLISON AUBREY, BYLINE: We're all familiar with the concept of calories in-calories out. If you burn off what you eat, this is the key to a healthy weight. But what if the way our bodies use or burn calories is significantly influenced by how many good hours of sleep we get each night? Researcher Helene Emsellem says over the last few years, evidence has been gathering that this is the case. The role of sleep is quite important.
HELENE EMSELLEM: There is a building body of literature that shows that there is an intimate relationship between the amount of sleep we get and our ability to maintain a good, healthy body weight.
AUBREY: It's been documented that people who go through long periods of sleep interruptions, such as parents of newborns and shift workers, are at risk of gaining weight or of having a harder time taking it off. And researcher Matthew Brady of the University of Chicago and his colleagues wanted to know why, what's actually happening in the body? In order to study this, they recruited a bunch of young, healthy volunteers who agreed to sleep a total of eight nights in a sleep lab.
MATTHEW BRADY: So they were admitted into the sleep lab at the university and for four nights they were allowed to stay in bed for eight and a half hours per night and then we got a sample of their fat after that intervention.
AUBREY: Then a month later, they came back to the sleep lab for four more nights. This time, they were only allowed to stay in bed for a much, much shorter period, just four and a half hours a night. And Brady says their fat cells responded dramatically.
BRADY: I was very surprised, to be honest. What we found is that just four nights of four and a half hours of sleep in bed was enough to reduce insulin sensitivity in the fat cells by 30 percent, which is actually quite a marked reduction.
AUBREY: And it's exactly what you do not want to happen in your body. Brady explains, two things happen when fat cells become less responsive to insulin.
BRADY: The first is that fat cells are actually your friend. They are there to safely store away lipids inside the fat cell. And as long as the lipids stay inside the cell, everything's fine and your body can utilize that energy when you're exercising or sleeping. However, when fat cells become insulin resistant, the lipids start to leach out of the fat cells and then they rise in the circulation and they start to accumulate in other tissues in the body.
AUBREY: Such as in the liver, where it can lead to fatty liver disease and the skeletal muscle, where it interferes with the body's ability to clear sugar from the blood into the muscle. And this is a problem, because it can set the stage for a range of metabolic problems, including type two diabetes and weight gain.
Now, the young healthy volunteers in the study most likely rebounded after returning to their normal sleep patterns. But over a lifetime, sleep expert Helene Emsellem says this new line of research challenges the assumption that we can control our weight solely by watching how much food we take in.
EMSELLEM: And what the message is in this article is that your body may decide to store more of that food as fat if you haven't gotten enough sleep.
AUBREY: In our society, where about 20 percent of us routinely get six or fewer hours of sleep per night - and many, many more fall short of the seven to nine hours recommended - Emsellem says perhaps a study like this will nudge more people to make sleep a priority.
Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.