Medically Approved

How your internal clock affects your health

Woman waking up to her alarm clock

Optum Perks Author

By Optum Perks Author

Have you ever wondered why it’s so hard for our bodies to adjust to major time differences? Whether we’ve flown to another time zone, or another country for that matter, or simply had to get up several hours earlier for a work meeting, most of us can instantly feel the effects of the change. We tend to become more irritable than normal and have a harder time getting through the day as our body’s way of trying to cope with being “off.”

But there’s more at work than just a simple matter of lack of sleep. When we dramatically change our sleeping and waking patterns, we’re actually causing a shift in our circadian rhythm. Also known as our internal clock or our sleep/wake cycle, all animals and some plants function based on their circadian rhythm. It’s an important part of our biology and can have negative consequences if it’s not cared for and maintained.

How Does It Work?

Our circadian rhythm is a complex process involving tens of thousands of nerve cells in a part of our brain called the hypothalamus. Since our internal clock is largely regulated by periods of light and dark, along with other factors in our body, our eyes transmit this information to the hypothalamus and influence how our body is perceiving the time of day.


Most individual’s circadian rhythm has a specific set of peaks and valleys, where we feel more tired during the middle of the night and the middle of the afternoon, generally between 2:00 and 4:00 am and pm. Given that these times are fairly regulated for the average person, it’s easy to see how changing time zones or abiding by an unusual work schedule could cause disruption to one’s sleep/wake cycle.

What’s Happening In Your Body

More than just our sleep schedules can be attributed to the circadian rhythm; rather, a handful of chemical reactions are able to take place in our body thanks to the response from our hypothalamus. When our body senses less light around us, the hormone melatonin begins ramping up production so that we’ll be able to fall asleep soon.


Body temperature also mirrors the schedule of our circadian rhythm, although no direct links have been made. Hunger and metabolism are also largely influenced by our internal clock, as well as how our body handles inflammation and stress.

Your Clock Affects The Big Picture

Going on vacation across the globe or waking up early every once in a while isn’t a cause for concern, as our circadian rhythm can bounce back pretty naturally. What’s concerning is the constant disruption in our cycle, like when individuals travel extensively or have to work odd hours for long periods of time.


Your health can suffer if your internal clock is constantly trying to figure out what’s going on, and many people can experience the following concerns:

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  • Some could have an increased risk of cancer, as melatonin naturally prevents the development of tumors
  • You might see changes in your weight, as the chemicals that regulate hunger and fullness can become confused due to irregularities to your internal clock
  • An increased risk of diabetes and heart disease has been found in those whose sleep schedules are erratic
  • Weakened immune systems might stem from an interrupted circadian rhythm
  • Those with confused internal clocks might find it more difficult to learn and retain information and might see their creativity lapse

Fixing Your Disrupted Clock

Just because your circadian rhythm has been affected by your lifestyle doesn’t mean that you are forever relegated to feeling tired and will be at a higher risk for health concerns. New research has shown that you can have a huge impact on auto correcting your sleep/wake cycle through your exercise and eating patterns.


It’s long been advised from friends, family, and sometimes even medical professionals that exercising in the evening time can have negative impacts on your sleep, yet experts are now stating the opposite. The Director of the Division of Sleep Medicine at Harvard notes that exercising at night doesn’t keep you awake for hours like many once thought. The real culprit is eating dinner later at night, which can confuse your hormones and your hypothalamus.

On a larger scale, the times during which we eat can play a huge part in letting our circadian rhythm know where it should be during its 24-hour cycle. Studies have recently shown that shifting your mealtimes can create a change in your internal clock, which is often sage advice given to those who want to beat jet lag.

If you’re constantly feeling “off” and find that your sleep might not be as restful or consistent as it could be, you might consider that your symptoms stem from your circadian rhythm needing to be reset. Try going to bed and waking at the same times each night and day as well as eating meals at regular intervals. Before you know it you’ll feel back to your old self again!