By Satchin Panda, PhD

Sleep is the most important rhythm to maintain. We need continuous, uninterrupted sleep for 6 to 8 hours every night, and this sleep should begin and end at a consistent time. If this rhythm is disrupted, it has bad effects that reverberate throughout the brain and body. 

For instance, exposure to light when we should be sleeping can disrupt the suprachiasmatic nucleus (SCN)—region of the brain responsible for controlling circadian rhythm. This disruption subsequently affects other rhythms in the brain and several hormone rhythms in the body. And, when your sleep rhythm is thrown off for even a few days in a row, every organ suffers. The digestive system is affected, leading to indigestion, and exacerbating any digestive issues that diabetics suffer from, including gastroparesis. 

The heart may not work well; a 2014 study showed that one hour of sleep deprivation during the “spring forward” to Daylight Saving Time raised the risk of having a heart attack the following Monday by 24 percent, compared to other Mondays during the year.¹ The immune system may also become too reactive or too insensitive without the right amount of sleep, increasing our risk for developing an infection (and diabetics are typically more prone to infection). 

Loss of sleep also makes our brain foggy, which leads to making poor health decisions. For instance, the brain actually craves sugar for energy, and poor food choices that lead to excessive sugar intake can cause the metabolism to be thrown off-balance. Studies have shown that as few as four or five nights of poor sleep (that is, sleeping 5 hours or less) can raise a person’s blood glucose by several points, leading to an otherwise healthy person possibly being misdiagnosed as prediabetic.^{2, 3}

Reduced sleep also confuses the brain hormones that regulate hunger. The brain cannot predict how long a person is going to stay awake, and since staying awake requires more energy than sleeping, the brain increases its production of the hunger hormone. As a result, people always eat more than what is needed to stay awake for just a few extra hours. 

Sleep deprivation confuses the brain, making us choose unhealthy foods over healthier options. We crave energy-dense foods when we are overtired, and overeating those foods ultimately contributes to obesity and diabetes. Sleep deprivation also makes us lethargic and less active, which further contributes to excessive energy storage and leaves us with one less tool to control our blood glucose.

Physical Activity for Blood Glucose Control

When we’re not eating or sleeping, we’re supposed to be engaged in some form of physical activity. Our metabolism and physiology evolved so that our body can perform physical activity throughout our wakeful hours, from morning to evening. In particular, we are designed to be more active in the morning and again in the late afternoon and evening. Each of these activity windows serves a role in controlling blood glucose. 

The first activity window is at dawn. Outdoor exercise with exposure to the morning light, picked up by the SCN and rest of the brain, is effective in suppressing the sleep hormone melatonin, which keeps the pancreas asleep. With reduced melatonin, the early daylight primes the pancreas to produce enough insulin to take care of the glucose rush after breakfast. 

In the afternoon, increasing our physical activity serves two purposes. It burns some stored glycogen from the muscles, and it primes the muscles to absorb the sugar that will come from dinner. Priming the muscles is necessary because the pancreas gets tired at the end of the day and may not produce enough insulin to take care of the glucose rush that comes with an evening meal. 

Physical activity can make our muscles act like a sponge, soaking up blood glucose without the help of insulin—so much so that even people with Type 1 diabetes, who do not produce insulin, can reduce the amount of insulin they need to maintain their blood glucose by being physically active. For those with Type 2 diabetes, even a 10- to 15-minute brisk walk or ride on a stationary bike after dinner is effective in reducing blood glucose to normal levels. In this sense, physical activity after a meal is almost like having an extra boost of insulin or an extra dose of diabetes medication. Compared to medicine, exercise is free and has only positive side effects.

Some people with diabetes find that exercise can increase their blood glucose levels. This can be alarming, especially if you also have an unexplained tendency to see a gradual rise in blood glucose in the morning. 

Those who do see an increase in blood glucose in the morning should exercise in the evening, either before or after dinner, so that they don’t have such an alarming increase in blood glucose.

If you haven’t been diagnosed with diabetes and you are currently mostly sedentary, any exercise at any time of the day is good. However, if you are already active and want to optimize your exercise timing, stick with late afternoon or early evening, when your muscles and joints are more flexible and therefore you have less chance of injury.

Physical activity is also the best way to spend the extra energy we gain from overeating. Although the brain uses mostly glucose as its energy source, we cannot make our brain “spend energy” by thinking extra hard. You could turn off the heater or sit outside on a cold day with no winter clothing to burn some calories to keep the body warm, but that’s just not efficient. Exercising for at least an hour daily can burn between 200 and 500 calories, creating an energy deficit you can count on for managing weight.

Exercise also has indirect benefits, including better sleep. As we discussed earlier, getting better sleep also reduces the craving for unhealthy food. What’s more, exercise encourages the muscles to produce many biochemicals and hormones that improve the function of other organs, including the brain. Yet while we know that exercise is good for us, there is no mechanism that drives us to be physically active. To keep yourself aligned with your circadian rhythms, you have to make time to be active every day.

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Satchin Panda, PhD, is a leading expert in the field of circadian rhythm research. He is a professor at the Salk Institute and a founding executive member of the Center for Circadian Biology at the University of California, San Diego. Panda is a Pew Scholar and a recipient of the Julie Martin Mid-Career Award in Aging Research.

Adapted from The Circadian Diabetes Code copyright © 2021 by Satchidananda Panda, PhD. Used by permission of Rodale Books, an imprint of Random House, a division of Penguin Random House LLC, New York. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.

This article is from the Spring 2022 issue of Well Being Journal

References

Sandhu A, Milan S, Gurm HS. “Daylight Savings Time and Myocardial Infarction.” Open Heart 2014;1(1):e000019.

Eckel RH, Depner CM, Perreault L, Markwald RR, Smith MR, McHill AW, Higgins J, Melanson EL, Wright KP Jr. “Morning Circadian Misalignment During Short Sleep Duration Impacts Insulin Sensitivity.” Curr Biol. 2015 Nov 16;25(22):3004–10.doi: 10.1016/j.cub.2015.10.011. Epub 2015 Nov 5.

McHill AW, Wright KP Jr. “Role of Sleep and Circadian Disruption on Energy Expenditure and in Metabolic Predisposition to Human Obesity and Metabolic Disease.” Obes Rev. 2017 Feb;18 Suppl 1:15–24. doi: 10.1111/obr.12503.