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.