Anyone who has suffered from jet lag or struggled after moving the clock forward or back an hour for daylight saving time knows all about what researchers call your biological clockor circadian rhythm – the “master pacemaker” that synchronizes how your body responds to the transition from day to day.
This “clock” is made up of approximately 20,000 neurons in the hypothalamus, the area near the center of the brain that coordinates your body’s unconscious functions, such as breathing and blood pressure. Humans are not the only beings with an internal clock system: all vertebrates – or mammals, birds, reptiles, amphibians and fish – have biological clocks, as do plants, fungi and bacteria. Biological clocks explain why cats are most active at dawn and dusk, and why flowers bloom at certain times of the day.
Circadian rhythms are also essential for health and well-being. They govern physical, mental, and behavioral changes in your body during each 24-hour cycle in response to environmental cues like light and food. They are why more heart attacks and strokes occur early in the morning. This is also why the mice that are miss their biological clocks age faster and have a shorter life expectancy, and people mutation in their circadian clock genes have abnormal sleep patterns. Chronic misalignment of your circadian rhythm with external cues, as seen in night workerscan lead to a wide range of physical and mental disorders, including obesity, type 2 diabetes, cancer and cardiovascular disease.
In short, there is plenty of evidence that your body clock is critical to your health. And chronobiologists like me study how the day-night cycle affects your body to better understand how you can modify your behaviors to use your internal clock to your advantage.
How Biological Rhythms Affect Your Health
Your biological clock affects 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 to environmental light-dark cycles so that certain hormones are released in certain amounts at certain times of the day.
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 bedtime as it can disrupt melatonin secretion and sleep quality.
Your circadian rhythm also affects your metabolism. Among other things, sleep helps you regulate leptin, a hormone that controls appetite. Your leptin levels fluctuate throughout the day in a rhythm set by your circadian clock. Insufficient or irregular sleep can disrupt leptin productionwhich can make us hungrier and lead to weight gain.
In recent years, researchers have discovered even more ways your circadian clock can affect your health. For example, research now suggests that eating at fixed times of the day, or time-limited dietcan prevent obesity and metabolic diseases. Depression and other mood disorders may also be linked to dysfunctional circadian control that leads to changes in the way your genes are expressed.
The time of day when you take your medicine may also affect its effectiveness and the severity of side effects. Likewise, your biological clock is a potential target for cancer chemotherapy and anti-obesity treatments.
And finally, even your personality can be shaped by whether your internal clock makes you a “morning person” or an “evening person”.
Getting the most out of exercise
Circadian clocks also provide a potential response to the best time of day to maximize the benefits of physical exercise.
To investigate this, my colleagues and I took blood and tissue samples from the brain, heart, muscle, liver, and fat of mice that exercised either before breakfast early in the morning, or after dinner late at night. We used a tool called a mass spectrometer to detect about 600 to 900 molecules produced by each organ. These metabolites served as real-time snapshots of how the mice responded to exercise at specific times of the day.
We assembled these snapshots to create a map of how morning versus evening exercise affects each of the mice’s different organ systems – what we called a 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 exercising early in the morning lowered blood sugar more than exercising late at night. Late-night exercise, however, allowed the mice to benefit from the energy they had stored during their meals and increased their endurance.
Of course, mice and humans have many differences as well as their similarities. For one thing, mice are more active at night than during the day. Nonetheless, we believe our findings could help researchers better understand how exercise affects your health and, if timed appropriately, can be optimized for the time of day to achieve your health goals. personal.
Adapt to your biological clock
I believe the field of chronobiology is growing and we will produce even more research providing practical applications and insights into health and well-being in the future.
In my own workfor example, a better understanding of how exercising at different times of the day affects your body could help tailor exercise plans to maximize specific benefits for patients with obesity, type 2 diabetes and other diseases.
There is still a lot to learn about how your circadian clock works. But in the meantime, there are proven ways to synchronize their internal clock for better health. These include regular exposure to sunlight to trigger the endocrine system to produce vitamin D, staying active during the day to help you fall asleep more easily at night, avoiding caffeine, and reducing your exposure to artificial light before bedtime.
