STEVE INSKEEP, HOST:
Today in Your Health, we'll listen to the ticking of your biological clock. OK, not literally. It doesn't actually tick, but we do have internal mechanisms that regulate metabolism and even our behavior. This is a story we first told you back in 2015, which we revived today because three scientists have won the Nobel Prize in physiology or medicine for their research into how these clocks work. Here's NPR's Allison Aubrey.
ALLISON AUBREY, BYLINE: On a recent morning at about 7:30 when I'd normally be eating breakfast and starting my day, I meet up with a guy across town, Tom Washburn who's doing just the opposite. He's finishing his workday as an overnight hospital nurse.
TOM WASHBURN: I'm at the end of my shift and I'm tired. (Laughter). Yeah, I need to sleep. I'm dying.
AUBREY: The whole pattern of his life is upside down, and he's feeling it. He ate dinner some time after midnight last night.
WASHBURN: Sometimes my body just doesn't, you know, cooperate, I suppose. And I get tired, I get hungry, I get bloated, just, things - just, it feels off.
AUBREY: Now, it's not just shift workers and jetlagged globetrotters who override their natural circadian rhythms. To a lesser extent, it's also all those people who just can't turn off the iPad at night and have to drag themselves out of bed in the morning. Fred Turek is a circadian scientist at Northwestern University.
FRED TUREK: These people are totally out of synchrony. When their body clock is telling them to go to sleep, they have to be awake. And then when they try to go to sleep, their body clock is saying, hey, time to get up.
AUBREY: Now, Turek says we can certainly bounce back from a trans-Atlantic trip or an all-nighter, but when living against the clock becomes a way of life, lots of things go awry. Studies show if you mess with the body's sleep-wake cycle, your blood pressure goes up, hunger hormones get thrown off and blood-sugar regulation goes south. Over time, Turek says, this may set the stage for metabolic diseases such as diabetes.
TUREK: What happens is that you get a total de-synchronization of the clocks within us, which may be underlying many of the chronic diseases we face in our society.
AUBREY: Now, notice that Turek says clocks, plural, within us. We've known for a long time about the master clock in our brains that synchronizes our body to the 24-hour, light-dark cycle, but in recent years, scientists have made a pretty cool discovery. It turns out that we have different clocks in every organ.
TUREK: Yes, there are clocks in all the cells of your body.
AUBREY: Wow. It's kind of stunning.
TUREK: Yes. That is a discovery that's literally surprised us, I must say.
AUBREY: Turek says think of all these clocks in our bodies as instruments or players in an orchestra.
TUREK: The idea that the heart has a clock.
AUBREY: Think of it as a drum.
(SOUNDBITE OF BEATING DRUM)
AUBREY: And the kidneys?
TUREK: The kidneys have a clock - two clocks, one in each kidney.
AUBREY: Maybe they're the horns.
(SOUNDBITE OF BLOWING HORNS)
AUBREY: Then there's the pancreas.
TUREK: Yes, the pancreas has a clock.
AUBREY: That's the flute.
(SOUNDBITE OF FLUTE PLAYING)
AUBREY: Now, the master clock in our brains is like the symphony conductor keeping all of the players in sync.
(SOUNDBITE OF VIOLINS TUNING UP)
TUREK: Once the conductor comes on, everybody's in synchrony and it sounds beautiful.
(SOUNDBITE OF SYMPHONY PLAYING)
TUREK: The idea that your body is functionally - normally when everybody's in synchrony with the master conductor in your brain.
AUBREY: You're sleeping well, eating regularly and feeling good. But what if the clocks get out of sync?
(SOUNDBITE OF DISJOINTED ORCHESTRA)
TUREK: (Laughter). It sounds - you sound so bad, right?
AUBREY: And, Turek says, something like this may happen in our bodies. So think back to Tom, the overnight nurse. The master clock in his brain, which is set by the 24-hour, light-dark cycle, is like the conductor cueing all the other clocks in the body that it's night. So for example, his digestive organs are not expecting food.
TUREK: The clock in the brain is sending signals out. Do not eat. Do not eat.
AUBREY: And this is where things get out of whack.
(SOUNDBITE OF DISJOINTED ORCHESTRA)
AUBREY: Tom has to eat something on his overnight shift, and when he does, research suggests this meal may reset the clock in his digestive organs. So instead of being in sync with the master clock, the clock in, say, the pancreas, which has to start releasing insulin to deal with the meal, is getting competing time cues.
TUREK: The pancreas is listening to the signals related to food intake, but that's out of synchrony with what the brain is telling it to do. So if you are sending signals to those organs at the wrong time of day, such as eating at the wrong time of day, we're upsetting the balance.
AUBREY: Now, it's still early days for circadian science. But there's growing evidence that different organs and systems in the body are programmed to do different things at different times. For instance, doctors have long known that the time of day you take a drug can influence its potency, and Turek says part of this is that the liver may be better at detoxifying at certain times of day.
TUREK: You take a drug at one time of day, it might be much more toxic than at another time of day.
AUBREY: And consider a recent weight-loss study by a circadian scientist at Harvard named Frank Scheer. He found that the timing of meals may influence how much weight people can lose.
FRANK SCHEER: The finding was that people who ate their main meal earlier in the day were much more successful at losing weight.
AUBREY: In fact, early eaters lost 25 percent more weight than later eaters.
SCHEER: So quite a surprisingly large difference.
AUBREY: Now Northwesterners Fred Turek says his hope is that down the road circadian science will make a big difference to the practice of medicine.
TUREK: We would like to be in a position where we'd be able to monitor hundreds of different rhythms in your body and determine if they're out of synchrony with each other, and then we would try to normalize them.
AUBREY: Now, whether or how quickly this may happen is hard to say. But what is clear is that the study of the biology of time is exploding.
TUREK: What we're doing now in medicine is what Einstein did for physics at the beginning of the last century. He brought time to physics. We are bringing time to biology. That's - that's new.
AUBREY: The irony is that this insight comes at a time when more and more of us seem to be ignoring our internal clocks. Allison Aubrey, NPR News.
(SOUNDBITE OF PIANO PLAYING)
INSKEEP: Comes at a time when we're ignoring our clocks? That's what she said. If you're having a hard time imagining all these clocks ticking away inside you, we have an animated explanation at NPR's health blog, Shots, which is available any time, day or night. Transcript provided by NPR, Copyright NPR.