When time shifts, remember your body has a clock, too

Today's the day most of us in the United States switch back from daylight saving time to standard time — giving ourselves a 25-hour day and commanding the sun to rise and set an hour earlier than it did yesterday.

At least that's how it looks on the clocks in our homes. The clocks in our bodies know better — and will be telling us we are hungry for dinner and ready for bed early tonight. Those effects are benign compared to what happens when we lose an hour of sleep to start daylight saving time again in the spring: heart attacks increase for several days after that, studies show.

Consider these twice-yearly time changes a reminder: Your body is keeping time, all the time.

"Without even paying attention to it, our lives are timed on the day-night rhythm," following a master clock in our brains and time-keeping cells throughout the body, says Paolo Sassone-Corsi, director of the Center for Epigenetics and Metabolism at the University of California-Irvine. "All our physiological and metabolic functions are cyclic: the sleep-wake cycle, the feeding rhythm, the body temperature and so on."

Yet we live in a world where it is often possible to ignore clocks, internal and external, thanks to indoor lighting and always-on electronic devices.

That's not healthy, experts say. You will feel better, sleep better and maybe even avoid some diseases if you live in sync with your body clock and keep your clock in sync with the sun. Here are a few ways to do that:

• Make sleep routine. Getting enough sleep is important. But sleeping and waking at the same time each 24 hours may be just as important, says Charles Czeisler, chief of sleep medicine at Brigham and Women's Hospital, Boston. "Sleep has a structure," he says, and it is best maintained with a predictable rhythm. Disturb the rhythm and you may find yourself struggling to sleep, hard to awaken and tired all the time.

• Night owl or lark? Some people, born night owls, feel best staying up past midnight and waking mid-morning; others, natural morning larks, prefer an early-to-bed, early-to-rise routine. If you can, choose a schedule that lets you work when you are most alert, sleep when you are tired and wake refreshed, says Natalie Dautovich, an environmental scholar with the National Sleep Foundation and an assistant professor of psychology at the University of Alabama.

• Seek the morning light. Whenever you get up, seek out bright light. Outdoor light is most powerful, but breakfast in a well-lit kitchen, near a window, will do. Pre-dawn risers and those prone to depression, especially in winter, may want to get a light box that mimics morning sunlight. Morning light "serves as an alerting signal to the body clock" that another day has commenced, Dautovich says.

• Dim the evening light. Too much light at night can suppress melatonin, a hormone that promotes sleep. Especially disruptive: the blue light from TV, computer, tablet and phone screens and from some energy-efficient light bulbs, Czeisler says. Glasses that block blue light or software that changes screen color and brightness might help, but experts say the best idea is to get away from screens in the hour or two before bed. In the evening, you also should use light bulbs on the warmer end of the color spectrum, Czeisler says.

• Have a bedtime routine. "Read a book, take a warm bath, whatever helps you relax," says Shalini Paruthi, director of the Pediatric Sleep and Research Center at SSM Cardinal Glennon Children's Medical Center, St. Louis. Such routines can trigger sleepiness in everyone from infants to elders, she says. If you have trouble stopping other activities to get ready for bed, she suggests setting a go-to-bed alarm.​​​

• Avoid midnight snacks. Eating late at night, especially after melatonin release begins, has been linked with increased risk of diabetes and obesity, Czeisler says. The body seems to metabolize food differently at different hours. "A burger at noon could be OK, but the same burger at midnight is not," Sassone-Corsi says.

• Beware shift work. Shift workers break all the rules of body-clock maintenance — changing their sleeping and eating schedules and getting light at odd hours — and appear to pay a health price. Studies suggest links with cancer, heart attacks, workplace injuries and depression, as well as diabetes and obesity. While it might not be possible to abolish shift work, "awareness needs to increase," and studies on health solutions need to be done, Sassone-Corsi says.

Reset your body clock

While individual body clocks and scheduling needs vary, here's how someone who rises around 7 a.m. might stay in sync with their natural rhythms.

7 a.m. Get up at the same time each day.

7:15 a.m. Get some light as soon as possible.

1 p.m. Cut off caffeine in the afternoon.

8 p.m. Avoid bright lights.

10 p.m. Get away from electronic devices.

11 p.m. Follow a bedtime routine.

12 a.m. Avoid midnight snacking.