biological clock: How your biological clock affects your health – all based on time of day


Anyone who has suffered jet lag or has had difficulty adjusting their clocks an hour ahead or back to achieve Daylight Savings Time knows all about what researchers call your biological clock, or circadian rhythm – the “master pacemaker” that synchronizes your body’s response. for the passing hours. one day to another.

This “clock” is made up of about 20,000 neurons in the hypothalamus, an area near the center of the brain that coordinates your body’s unconscious functions like breathing and blood pressure. Not only humans have an internal clock: all vertebrates, mammals, birds, reptiles, amphibians, and fish have a biological clock, as well as plants, fungi, and bacteria. The biological clock explains why cats are most active at dawn and dusk, and why flowers bloom at certain times of the day.

Circadian rhythms are also important for health and well-being. They govern the physical, mental and behavioral changes in your body during each 24-hour cycle in response to environmental cues such as light and food. This is why more heart attacks and strokes happen early in the morning. They also cause mice lacking a biological clock to age faster and have shorter lifespans, and people with mutations in circadian clock genes have abnormal sleep patterns. The chronic misalignment of your circadian rhythm with external cues seen in night shift workers can lead to a wide range of physical and mental disorders, including obesity, type 2 diabetes, cancer, and cardiovascular disease.


In short, there is ample evidence that your biological clock is critical to your health. And chronobiologists like me study how the cycle of day and night affects your body to better understand how you can change your behavior to use your internal clock to your advantage.

How biological rhythms affect your health
Your biological clock influences your health by regulating your sleep-wake cycles and fluctuations in blood pressure and body temperature. It does this primarily by synchronizing your endocrine system with the cycles of light and dark in your environment so that certain hormones are released in certain amounts at certain times of the day.

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The pineal gland in your brain, for example, produces melatonin, a hormone that helps regulate sleep in response to darkness. Doctors advise reducing exposure to artificial blue light from electronic devices before bed because it can interfere with melatonin secretion and sleep quality.

Your circadian rhythm also affects your metabolism. Among other things, sleep helps regulate levels of leptin, a hormone that controls appetite. Leptin levels fluctuate throughout the day according to the rhythm set by your circadian clock. Inadequate or irregular sleep can disrupt leptin production, which can make us hungrier and lead to weight gain.

In recent years, researchers have discovered even more ways your circadian clock can influence your health. For example, research is currently underway suggesting that eating at certain times of the day or time-restricted feedings can prevent obesity and metabolic disease. Depression and other mood disorders can also be linked to a disruption in circadian control, resulting in changes in your gene expression.


The time of day you take your medicine can also affect how well it works and how bad the side effects can be. Similarly, your biological clock is a potential target for cancer chemotherapy and obesity treatments.

And finally, even your personality can be affected by whether your internal clock makes you a morning person or a night light.

Getting the most out of exercise

The circadian clock also provides a potential answer to the question of when is the best time to get the most benefit from exercise.


To study this, my colleagues and I collected blood and tissue samples from the brain, heart, muscle, liver, and fat of mice that exercised either before breakfast in the early morning or after dinner in the late evening. We used an instrument called a mass spectrometer to detect approximately 600 to 900 molecules produced by each organ. These metabolites served as real-time snapshots of how the mice responded to exercise at certain times of the day.

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We combined these images together to create a map of how morning and evening exercise affected each of the mice’s various organ systems—what we called the exercise metabolism atlas.

Using this atlas, we saw that the time of day affects how each organ uses energy during exercise. For example, we found that early morning exercise lowered blood glucose levels more than late evening exercise. However, exercising late in the evening allowed the mice to benefit from the energy they had stored while eating and increased their endurance.


Of course, mice and humans have many differences along with their similarities. First, mice are more active at night than during the day. However, we believe our results can help researchers better understand how exercise affects your health, and if timed correctly, it can be optimized based on the time of day to achieve your personal health goals.

How to get along with your biological clock

I believe that the field of chronobiology is growing and we will be doing more research that provides practical applications and understanding of health and wellness in the future.

In my own work, for example, a better understanding of how exercising at different times of the day affects your body can help tailor exercise plans to maximize specific benefits for patients with obesity, type 2 diabetes, and other conditions.

We still have a lot to learn about how your circadian clock works. But at the same time, there are several proven ways to synchronize your internal clock for better health. These include regular sun exposure to force the endocrine system to produce vitamin D, staying active during the day to make it easier to fall asleep at night, avoiding caffeine, and reducing exposure to artificial light before bed.

(This PTI was syndicated through The Conversation)


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