Returning to “standard time” is better for our health, according to sleep scientists, but the time change can be disruptive, and our bodies also need to adjust to more hours of darkness as we approach winter.
The body is a sophisticated timekeeping machine. And growing evidence shows that if you align your daily habits with your circadian rhythms—including when you sleep, eat, and exercise—you can help prevent chronic diseases and optimize health.
Let’s start with a brief introduction: “Your body is full of clocks,” explains Emily Manoogian, a researcher and chronobiologist at the Salk Institute for Biological Studies. In addition to the master clock in your brain, there are timekeeping mechanisms in every organ and in your cells.
“Every cell in your body that has DNA has a molecular clock that keeps its own time,” she says. They all are part of your body’s circadian system, helping you stay synchronized with the 24-hour cycle. But our bodies don’t maintain a perfect rhythm on their own. Every day, we drift a little from the 24-hour cycle and need a reset, explains Satchin Panda, a researcher at the Salk Institute and author of “The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight.”
“The master clock in your brain coordinates all the other clocks through a series of different signals,” explains Manoogian, including external signals—like light, food, and movement. And that’s why the timing of when we perform our habits can play a fundamental role in synchronizing our clocks.
Sunlight serves as an external signal to resynchronize the master clock. That’s why it’s helpful to open the blinds in the morning and spend time outdoors.
And, it turns out, our first bite of food each day also acts as an external signal to synchronize the clocks in our digestive system and throughout the body.
“Food is also a signal to reset biological clocks, especially the one in the gut,” says Manoogian. “That’s one of the reasons why making sure you’re eating at the right time in relation to light is important.”
Eating is a signal to activate the digestive and metabolic organs, which are primed to function better during the day. At night, the metabolic system is also ready to rest.
“When you’re sleeping, your body expects to fast. And therefore, it deactivates the part of the system that takes glucose from the blood and stores it,” she explains.
When people eat too close to bedtime or in the middle of the night, their metabolic organs aren’t optimized to function properly. This misalignment can lead to poor blood sugar control. Her research shows that restricting the number of hours you eat during the day to a window of about 10 hours can lead to significant improvements in metabolic health.
There is much evidence that eating out of sync with circadian rhythms can increase the risk of metabolic diseases, including diabetes and obesity. Studies show that shift workers, including those on night shifts, have a higher risk of developing these conditions, in part due to disruption of natural rhythms.
And when it comes to exercise, some people feel better in the morning, others in the afternoon, says Dr. Phyliss Zee, director of the Center for Sleep and Circadian Medicine at Northwestern University’s Feinberg School of Medicine. But science shows that exercising late at night, shortly before bed, can disrupt sleep.
“There is a peak time for almost all physiological processes,” says Zee. “The timing of meals, the timing of exercise, physical activity—all of that helps synchronize the body’s biological clocks,” she states.
If you dine and go to bed approximately at the same time most nights, your habits can be beneficial. “Science shows that regularity is very important for the circadian system and for health,” Zee concludes.
Although each person is unique, she says a general rule is to start limiting exposure to light, food, and intense exercise a few hours before bed.
But as scientists learn more about the importance of keeping our biological clocks synchronized, society has been moving in the opposite direction. Manoogian cites ads for midnight food menus and 24/7 work and entertainment as examples of our nonstop modern life.
One way to resist this is to monitor your daily habits. Michelle Pittsley, who lives in Vista, California, started using an app called myCircadianClock to log her eating and blood sugar. She says it helped her follow a time-restricted eating window and track her progress. The app was developed by Salk Institute scientists as a research tool and is used in Salk studies. It’s free for any adult who downloads it. The app provides guidance on when to sleep, eat, and exercise. (Note: When you sign up, you will be sharing data with researchers.)
When our circadian rhythms are “dysregulated,” the risk of chronic diseases increases, including obesity, diabetes, heart disease, fatty liver disease, intestinal diseases, and common types of cancer, say Panda and Manoogian. If you want to align your habits for better health, here are three strategies to try.
1. Eliminate late-night snacking and limit your eating window
People who restrict their eating to a 10-hour window can reduce their risk of type 2 diabetes, says Manoogian. She and Panda co-authored a study with 108 adults, average age 59, who had symptoms of metabolic disease. They found that those who followed time-restricted eating had a significant reduction in hemoglobin A1c (which is a person’s average glucose level over a few months), compared to participants who didn’t restrict their eating window.
Participants weren’t instructed to reduce calories, just to restrict the eating period for three months.
“It was exciting to see that just time-restricted eating was able to reduce the risk of type 2 diabetes by 60%,” says Manoogian, because sustained lower blood sugar reduces the risk of the disease.
Research also suggests that having the largest meal of the day in the afternoon, rather than late at night, can be beneficial for those who want to lose weight. A Spanish study found that those who ate dinner earlier lost 25% more weight than those who ate later. Panda says that when his mother stopped eating a late-night snack, which included tea with sugar and milk, and an occasional snack, that simple change led to a significant drop in her blood sugar levels.
2. Go to bed approximately at the same time most nights
“Maintaining the same sleep schedule is ideal,” says Manoogian. Consistency gives the body a chance to anticipate and keep biological clocks synchronized. During sleep, waste is cleared from the brain, memories are consolidated, and there is much evidence showing that rest is essential for our health.
But don’t blame yourself if you have a restless night. And, of course, there will be disruptions due to travel, work deadlines, or weekend celebrations. “Getting out of your circadian rhythm isn’t like breaking an arm,” says Manoogian. Think of the harms of irregular schedules like erosion from dripping water. “Small impacts, repeatedly, can wear down the system,” she says. And the result is that you may feel slower and older.
There are many bedtime rituals that promote a good night’s sleep, including limiting light before bed and sleeping in the dark. Zee’s research shows that even small amounts of light during sleep can have adverse effects on cardiovascular and metabolic health.
3. Exercise at your ideal time, but not too late at night
Whether you’re a morning person or a night owl can influence your ideal exercise time, so it varies from person to person, says Zee. “The best time to exercise depends in part on what we call chronotype,” she says, which is a person’s innate preference for sleep timing or when they feel most alert and energetic. One way to estimate your tendency is with a morningness-eveningness questionnaire.
“If you’re a morning person, then morning exercise can be beneficial,” creating a consistent structure, says Zee, but people who get more alert later in the day may want to postpone it. As people juggle competing obligations, exercise can be squeezed into the available slot in their schedule, even if it’s not their clock’s preferred time. She says it’s important to remember that exercise is beneficial, regardless of when you do it.
But keep this in mind: “Exercise is a stimulating signal to tell your body you should be awake,” says Manoogian, so it’s no surprise that recent research shows exercise shortly before bed can impair sleep quality.
Source: npr.org by Allison Aubrey