Researchers believe the clock controls everything from body temperature to pain relief.
If you have to drag yourself out of bed to exercise, your body may be telling you something.
Medical research shows that exercise is easiest when the body temperature is high. That is in the afternoon to early evening.
"The gym packs up between 5 and 7 [p.m.] in here, and that's about where your peak with your body temperature is," says fitness trainer Chris Mondragon.
A sundial uses sunlight to tell time -- it is Mother Nature's clock, and it acts a lot like our internal body clock which rises with the sun and sleeps when the sun sets. The problem is, we do not always listen to it.
"Sleep appears to have some restorative features, especially for the brain," says Dr. Bradley Vaughn, a UNC neurologist.
Doctors who study sleep patterns say it helps them better understand how the body's internal clock works.
The sleep-wake cycle is an important part of our body's daily rhythm.
"I think as a group, we are becoming more aware of the fact that this rhythm within the 24-hour day can be used to our advantage," says Vaughn.
One way doctors use the body clock is to prescribe medicine during times of the day when it will be most effective.
For example, symptoms of asthma and peptic ulcers increase at night, so doctors say it is best to take medication for them before bed.
"Timing medications to improve outcomes is something that many of us are looking into," says dentist Dr. Bill Wynne.
The best time to deal with pain is another thing doctors are looking into. Researchers say local anesthetics given to dental patients last longer in the afternoon, yet many dental surgeries are scheduled in the morning.
"We're all in the profession familiar with diurnal or circadian rhythms or natural body rhythms that play a part in even the way we practice medicine or dentistry," says Wynne.
The body clock does not always fit with our busy lives. Doctors say a morning workout is always better than no workout at all. And what works for your body clock may be different than what works for someone else.
The study of body rhythms is officially known as chronomedicine. For more information about how the body clock works, check out"The Body Clock Guide to Better Health"by Michael Smolensky and Lynne Lamberg.
Copyright 2023 by Capitol Broadcasting Company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.