Life Extension Magazine®

Man in bed sleeping working on his circadian code

Author Interview: Satchin Panda, PhD: The Circadian Code

Dr. Satchin Panda, author of The Circadian Code, explains that with some lifestyle modifications, you can restore balance to your circadian rhythm and reap long-term rewards in better sleep, greater health, and reduced risk of disease.

Scientifically reviewed by: Dr. Carol Campi, RN, DC, in August 2023. Written by: Jon Vanzile.

The idea that our waking and sleep cycles operate according to an internal clock called the circadian clock has been around for centuries, but it’s only been in the past few decades that we are learning the circadian clock does much more than control sleep.

According to Dr. Satchin Panda, author of The Circadian Code, our body plays host to innumerable internal clocks that control everything from our sleep to our mood to our gene expression and disease risk. Unfortunately, our modern world wreaks havoc with these circadian clocks. The combination of poor sleep hygiene, too much exposure to blue light, poor diet, and lack of activity at the right time of day throws our whole circadian system out of balance, resulting in increased vulnerability to a host of maladies from cancer to heart disease to depression. Worse yet, it only takes a few days of living out of balance to throw off our body’s well-regulated circadian clocks, says Dr. Panda.

There is good news, however. According to Dr. Panda, it’s easy to identify problems with your circadian clock, and with some lifestyle modifications you can restore balance to your circadian rhythm and reap the long-term rewards in the form of better sleep, greater health, and reduced risk of disease. In this exclusive interview with Life Extension®, Dr. Panda talks about his lifetime of work on the circadian rhythm and offers advice on how to restore balance to your life.

—Jon Vanzile

What you need to know

Author of The Circadian Code, Dr. Panda, in his new book, teaches us about the importance of our circadian rhythm. Circadian rhythms are biologic process exhibited by plants and animals (including humans) over the course of a day. These rhythms are governed by circadian biologic clocks contained in nearly all our cells that activate or deactivate genes at different times of day or night.

Image of DNA strand

LE: What is the circadian rhythm and how does it affect human health?

Dr. Panda: The term “circadian” comes from the Latin circa, meaning “around,” and “diem,” meaning “day.” Circadian rhythms are real biological processes that every plant, animal, and human exhibits over the course of a day. These rhythms are governed by internal circadian or biological clocks. Almost each and every one of our cells contains one of these clocks, and each is programmed to turn on or off thousands of genes at different times of the day or night.

These genes influence every aspect of our health. For instance, when we are healthy, we can have a good night’s sleep. In the morning, we wake up feeling fresh and energetic and ready to get to work. Our gut function is perfectly normal. We have a healthy hunger and a clear mind. In the afternoon, we have energy to exercise. At night, we are tired enough to go back to sleep without much effort. Having these rhythms is a sign of being healthy.

Yet when these daily rhythms are disturbed for as little as a day or two, our clocks cannot send the right messages to these genes, and our body and mind will not function as well as we need. If this disruption continues for a few days, weeks, or months, we may succumb to all types of infections and diseases, ranging from insomnia to attention deficit hyperactivity disorder, depression, anxiety, migraine, diabetes, obesity, cardiovascular disease, dementia, and even cancer.

LE: You discuss that there is not a single “circadian clock,” but that each organ system actually operates according to its own clock. Can you explain how that affects organ system health?

Dr. Panda: Circadian rhythms optimize biological functions. Every function in the body has a specific time because the body cannot accomplish all it needs to do at once. The circadian clocks interact with the timing of light, food, and activity to produce our daily rhythms. Our job is to maintain the clock so we can live with optimal health. The best way to do this is to live in accordance with the circadian clock, rather than push against it.

It begins with understanding the role light plays. The light sensors in our eyes are programmed to notice changes in the morning light and adjust our internal clock slightly by a few seconds or minutes every day. This “light entrainment,” or syncing the internal clock to the natural day/night cycle, enabled our ancestors to wake up at dawn, no matter the season.

In order to understand how light affects behavior, we need to focus on evolutionary biology, which traces our heritage back roughly 200,000 years. Primitive men and women had to wake up before the sun came up if they wanted to be successful hunters. They also had to have enough muscle tone in the late afternoon to run back the few miles they traveled away from the shelter in their search for food.

By the turn of the 20th century, electricity and light spread throughout the Western world, and food production became mechanized. After World War II, with all of these industrial systems in place, almost everyone in the industrialized nations started experiencing circadian disruption. Television, radio, and telephones began entertaining us late into the night. Today, the computer has taken the local evening fireside talk and transformed it into a real, yet virtual, global 24/7 chat session.

Yet while all of these advances are supposed to update the previous technology and make our lives better, they disrupt our body’s clock. Our circadian rhythm continues to be confused by bright light in the evening and limited access to natural light during the day. We simply have not evolved enough to sync our internal clock with the realities of the modern world. Constant exposure to light at night causes circadian disruption that suppresses sleep and leaves us hungry.

Although we have been living with circadian clocks for all of human history, we are just waking up to the key roles of circadian rhythms to stay healthy and prevent diseases. We have created lifestyles, work schedules, and technology without knowing how they affect our circadian rhythms. Now that we have a better understanding of circadian clocks, we can optimize our lifestyle and living environment to nurture circadian clocks and extend our healthy lifespan.

Two people eating

LE: How does this affect our genes?

Dr. Panda: Every gene in our genome has a circadian cycle. However, they don’t cycle at the same times, and some cycle only in one organ. This means that for every tissue there is a hidden time code to our genome. In a recent 2018 study, we found that up to 80% of all genes can be either turned on or off at different times of the day. Having a detailed knowledge of the action of genes and their timing has given us a clear understanding of how circadian rhythm optimizes cell function. For example, cellular repair and cell division is circadian. Our body is being repaired and rejuvenated every day, but this does not happen randomly. Rather, it occurs at a specific time of the day: at night, when we’re asleep. This is true for all different types of cellular systems.

LE: So all these systems work together? How can that knowledge help someone get healthier?

Dr. Panda: The clocks in different organs work like an orchestra to create three major rhythms that form the essential foundations of health: sleep, nutrition, and activity. These rhythms are entirely related and are also under our control. When they work perfectly, we have ideal health. When one rhythm is thrown off, the others are upset, creating a downward spiral of poor health.

For example, we are programmed to eat and sleep at certain times, but sometimes our habits and preference can interfere with this program. In fact, people who are “night owls” likely have bad habits, not any type of genetic issue. They often expose themselves to light, especially blue light from computer screens, late at night. However, when scientists took a group of these “night owls” who couldn’t fall sleep early and sent them on a camping trip into the wild, where they were exposed to regular daytime and nighttime light levels, their melatonin levels quickly became completely normal, with melatonin production starting earlier in the evening. Without access to bright light, these people were able to resume a more normal circadian rhythm and they were all able to get to sleep before 10 p.m. This experiment is one of the reasons I’m so convinced we are masters of our health. Correcting habitual behaviors is the key to improving your circadian code.

LE: This same principle works for nutrition and activity?

Dr. Panda: Absolutely. Just like the first light of the morning resets our brain clock, the first bite of the day resets our organ clocks. In fact, food timing can be a powerful cue to override the master clock. If you typically eat breakfast at 8 a.m., you’re setting an appointment with your stomach, liver, muscles, and pancreas, and they will be ready to process breakfast at 8 a.m. Breakfast becomes the cue that syncs the internal clock with your outside time. When you eat at 8 a.m., your system works optimally for about 8 to 10 hours. After a 10-hour window, the gut and metabolic organs will continue to work on food, but their efficiency slows down. So, if you’re wondering why diets haven’t worked, timing might be the reason. If you eat late at night, or start breakfast at a wildly different time each morning, you are constantly throwing your body out of sync. But don’t worry, the fix is equally simple: just set an eating routine and stick to it. The same is true of exercise. As each of us has a unique lifestyle and work schedule, in the book I explain how your current lifestyle may be working for or against your clock, and I guide you in Chapters 4–8 to an optimal timing of food, sleep, light, and exercise to stay healthy.

Man and woman jogging

LE: What kinds of benefits do people see from “fixing” their circadian rhythms?

Dr. Panda: It’s quite possible that some of the daily discomforts, frequent illnesses, or chronic diseases that people may have are linked to circadian disruption. The symptoms of many illnesses include poor or excessive sleep, change in appetite, or reduced physical activity. These are all disruptions to your circadian code. As outlined in Chapters 9–12, by fixing your rhythm, you can potentially correct your disease or lessen its severity, from digestive problems to cancer and dementia. Nurturing your circadian rhythm acts as a grand corrector of all maladies.

LE: What steps can people take to identify and correct their circadian rhythms?

Dr. Panda: If you are living with a medical condition, it is important to know if your condition may be disrupting your daily rhythms. In my book, The Circadian Code, I’ve developed quizzes you can take in the privacy of your own home to help you see if the quality of your circadian code is affecting your health. These quizzes assess how you’re feeling right now, and how far off you are from living within your optimal rhythm. After you take these, you’ll have the information you need to begin making adjustments to optimize your circadian system and benefit your health.

LE: If people do follow your advice, what kind of results can they expect?

Dr. Panda: If you are currently suffering from chronic illness, one of the best things you can do to reverse your course or lessen the severity is to enhance your circadian code. We are beginning to see many examples of people who are finding a whole new healthy lifestyle once they’ve tried this. Enhancing your circadian code isn’t a miracle cure, but by combining your doctor’s recommendations with this information, you will be doing everything in your power to be master of your own health.

A healthy circadian code prevents or reverses chronic illnesses and at the same time it boosts energy and vitality. As chronic illnesses are the major causes of death and disability, by preventing or reversing these diseases, we can expect to live a long healthy life.

The Circadian Code book
Item #34149

If you have any questions on the scientific content of this article, please call a Life Extension® Wellness Specialist at 1-866-864-3027.

Adapted from THE CIRCADIAN CODE: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight Copyright © 2018 by Satchin Panda, PhD. Published by Rodale Books, an imprint of Penguin Random House LLC.

To order a copy of The Circadian Code , call 1-800-544-4440 or visit