How to Use Your Internal Clock to Improve Your Health

Want to protect your heart, sleep better, and even drop a few pounds? It’s easy—if you tap into your body’s natural rhythms.

By Christie Aschwanden from Reader's Digest | August 2010

Birds do it. Bees do it. Even blue-green bacteria do it—tell time, that is, thanks to an internal clock that helps trigger migration, pollination, and, well, all those things that bacteria do. What’s even more surprising is that your body follows a clock, too, whether or not you wear a watch on your wrist. Your blood pressure, your stamina during exercise, and your tendency to sneeze or wheeze—just about every biological process sticks to some kind of daily or seasonal rhythm.

What that means: You can improve your health with barely any effort—if you know how to use the power of your body’s daily, weekly, and seasonal cycles. To feel better now, here’s the right time to …

1. Get the best medical care.

Have a cavity filled in the afternoon

The painkilling effect of dental anesthesia lasts longer in the afternoon than it does in the morning. In one study, lidocaine kept nerves numb up to five times longer when it was injected in the early afternoon compared with early morning.

Check your blood pressure in the morning and at night.

As a general rule, blood pressure fluctuates throughout the day—it hits its lowest point around bedtime and its highest when you wake in the morning, says J. David Glass, PhD, a circadian biologist at Kent State University. If you’re keeping an eye on your blood pressure to help your doctor decide whether you need medication, you could get an inaccurate picture by taking your reading just once a day. “If you’re measuring it yourself, it’s best to do it in the morning and evening,” Glass says. “Be sure to do it at the same times each day—don’t bounce around.” Taking the two readings could make the difference between your doctor prescribing blood pressure drugs and advising you to stick with diet and exercise, he says.

2. Drop a few pounds.

Weigh yourself on Friday and Monday

For those trying to lose weight, experts have long suggested stepping on the scale at least once a week—that’s the habit of most members of the National Weight Control Registry, every one of whom has taken off at least 30 pounds and kept it off for a year or more. Now a new study from the Washington University School of Medicine ratchets things up. Dieters tend to splurge on weekends, the research found—but a Friday weigh-in (especially done first thing in the morning, when your weight is lowest) provides positive feedback that can blunt the temptation to overeat, says lead study author Susan Racette, PhD. And getting back on the scale on Monday can help you correct your course quickly if you’ve strayed, she says.

Eat dinner earlier

Recent research supports the folk wisdom that nighttime eating is more apt to add pounds. In one study, researchers fed one group of mice during their normal waking hours and a second group when the animals usually slept. The mice that ate at the “wrong” time gained more than twice as much weight. “If you think you’re doing everything right with your diet but you’re not losing, try having dinner an hour earlier,” says lead study author Deanna Arble, at Northwestern University. “It won’t hurt, and it might help.”

Exercise in the evening

If you want to get fit faster, a late-day workout is the most efficient way to go. Research by Michael Deschenes, PhD, an exercise physiologist at the College of William & Mary in Williamsburg, Virginia, shows that strength and endurance climb by about 5 percent between 4 and 8 p.m., compared with morning hours, so you can push yourself harder. Your muscles are warmer, too, which will help you avoid injury.

3. Protect your heart.

Take preventive medicines in the evening

Research suggests that a daily aspirin is less likely to cause stomach bleeding when taken late in the day. It’s even possible that this timing could protect you better. The reason: Your risk of heart attack spikes in the morning (the danger is nearly three times higher between 6 a.m. and noon than during the rest of the day). Aspirin helps cut clot risk by reducing platelet “stickiness”—a single tablet will take care of a platelet for its entire ten-day life span. But new platelets are being made all the time. Taking your aspirin at night ensures that you’ll have plenty of the drug to defang newly minted platelets during those potentially dangerous morning hours.

Get an extra hour of sleep next time you set the clock ahead

Nothing says spring is coming like the hour of sunlight you gain when daylight saving time begins—but your heart might pay for that pleasure. Swedish researchers have seen a 5 percent jump in heart attacks during the first week of daylight saving time, probably because of the loss of sleep and the disruption of bodily cycles. Next year, it may be beneficial to get to bed earlier on the night you switch your clock.