Looking to run faster, sleep better, or lose weight? Here's how to align your body's circadian clock with your diet and workout schedule.
All day and all night, the master internal timer that is your circadian clock is ticking away, keeping virtually every bodily function on track. But from one minute to the next, your body is primed to respond to different functions and situations. “Your memory, energy level, metabolism, and even your chances of getting sick change throughout the day, often substantially,” explains Michael Smolensky, Ph.D., a professor at the University of Texas and coauthor of The Body Clock Guide to Better Health. The takeaway: Study up on these shifts and align them with your daily agenda and you may feel happier, healthier, and more productive.
Within 90 Minutes of Waking Up
Besides cranking your energy levels and revving your metabolism after the night’s fast, consuming about 300 calories first thing in the morning keeps you from getting ravenous and overeating later in the day, explains Joy Bauer, R.D., nutrition and health expert for the Today show. Shoot for a mix of complex carbs and lean protein, like egg whites and veggies in a whole-grain tortilla.
Before 10 a.m.
A 15-minute blast of UV light cues your brain to stop releasing the sleep hormone melatonin, chasing away that draggy just-woke-up feeling and improving your mood. Do apply sunscreen, though, says Albert M. Lefkovits, M.D., associate clinical professor of dermatology at the Mount Sinai School of Medicine.
Between 11 a.m. and 2 p.m.
When caving to your craving for a bag of chips is a given, this is the safest window. “If you go off your diet later in the day, there’s less time to burn the excess calories and get back on track before bedtime,” says Holly L. Phillips, M.D., a women’s health specialist in New York City and a CBS This Morning medical contributor.
While your fatigue level might not matter much (especially if you’re being sedated), you do want your doctor to be at the top of her game. “Studies show that surgeons make fewer mistakes in the morning, possibly because they’re more alert,” says Mark Di Vincenzo, author of Buy Shoes on Wednesday and Tweet at 4:00. For example, research from the Cleveland Clinic found that when physicians did colonoscopies in the a.m., they were more likely to catch something suspicious.
Between 12 and 2 p.m.
Even if you didn’t eat a heavy lunch, you may feel sleepy because body temperature naturally dips at this time—signaling that it’s time to rest, says Robert L. Matchock, Ph.D., associate professor of psychology at Penn State University. Cut through the fog with a 20-minute power walk.
Between 4 and 8 p.m.
Meet up with friends on the early side so that any alcohol will be metabolized before you hit the sheets—a process that could take several hours, especially if you have more than one glass. Otherwise, says Bauer, you’re likely to toss and turn and never experience deep, restorative slumber.
Between 5 and 6 p.m.
Body temperature is peaking—which means you’re more nimble and less likely to get injured—so it’s a good moment to experiment with a novel activity. “Hand-eye coordination is sharpest, lung functioning is high, muscle fibers are warm, and your mood is brighter,” says circadian rhythm expert Michael Smolensky. Matthew Edlund, M.D., author of The Power of Rest, agrees: “This is the time of day when Olympic records tend to be set.”
Before 8 p.m.
Late-night diners are at greater risk of packing on the pounds, according to a study from Northwestern University. Our bodies are designed to sleep when the sun goes down, so eating long afterward may cause changes in metabolism and insulin production that result in weight gain. After-dark digestion can also interfere with sleep, adds New York City–based nutritionist Stephanie Middleberg, R.D.
The chemicals that keep you from sweating are much better absorbed when your skin is dry, says Lisa J. Pieretti, executive director of the International Hyperhidrosis Society. “Most people put it on when their skin is still damp after a morning shower, but if you use it at night, it’ll plug your sweat ducts and help you stay fresh for 24 hours.”