Lack of Exercise Can Disrupt Your Body's Circadian Rhythm and Much More
June 26, 2015
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By Dr. Mercola
It’s been well-established that sleep is crucial for maintaining your circadian rhythm and has a significant bearing on metabolic disorders,1,2 not to mention optimal health in general.
But as it turns out, exercise may be just as important to keep your internal clocks in sync. Just as there is a time for being awake and being asleep, there are also times for physical movement and stillness.
As noted in a recent New York Times article:3
“Exercise may affect how and when we move, even when we aren’t exercising, according to a fascinating new study in mice.
The findings suggest that, by influencing our built-in body clocks, exercise may help our bodies to recognize the optimal times we should be moving, and when we should be still.”
The Biological Imperative of Movement
Research looking for clues about people’s natural movement patterns reveals that there appears to be “biological imperatives to movement” built into our system. One such study,4 published in 2009, found that people tend to move in logical intervals.
After a period of inactivity, they would start moving; once they’ve moved about or exercised, they would become inactive for a period. The intervals of movement and inactivity were more consistent in younger people than older ones. As noted in the featured article:5
“In essence, the young people’s bodies seemed to be somehow remembering and responding to what that body had just been doing, whether sitting or moving, and then calculating a new, appropriate response — moving or sitting.A more recent study6 looked at the movement pattern of mice, ranging in age from six months to two years—equivalent to a young adult’s and aging seniors in human terms.
In doing so, the researchers felt, the body created a healthy, dynamic circadian pattern.”
When running wheels were provided, the younger mice exercised a lot, developing marked peaks and valleys of activity. As in the human study, the older mice were less consistent in their activity patterns.
Once the running wheels were removed, the mice quickly fell into more random movement patterns, and the patterns of the younger mice became more like that of the older ones.
According to the researchers, this suggests that exercise has a far greater impact on your daily movement patterns than your age does. And, as noted in the featured article:
“Of course, exercise by definition influences how much activity someone completes during the day. But Dr. Scheer and his colleagues believe that something deeper and more interesting also occurs with exercise...
By prompting the release of a wide variety of biochemicals in the body and brain...exercise almost certainly affects the body’s internal clock mechanisms and therefore its circadian rhythms, especially those related to activity.
Exercise seems to make the body better able to judge when and how much more it should be moving and when it should be at rest.”
Exercise Reduces Mortality Risk
While that may seem like “no big deal,” exercise certainly has benefits that can make all the difference in the world—such as allowing you to live a longer. As Harvard Professor Dr. I-Min Lee told Reuters:7
“We have clear data showing that the more energy is expended, the greater the reduction in mortality rates.”One recent example of such data is a Norwegian study8,9,10 showing that when it comes to reducing mortality, regular exercise is as important as quitting smoking.
About 5,700 older men were followed for about 12 years in this study, and those who got 30 minutes of exercise—even if all they did was light walking—six days a week, reduced their risk of death by about 40 percent.
Compared to those who were inactive, those who engaged in moderate to vigorous exercise lived about five years longer, and physical activity was almost as predictive as smoking when it came to mortality risk.
According to the authors: “Increase in physical activity was as beneficial as smoking cessation in reducing mortality,” concluding that: “Public health strategies in elderly men should include efforts to increase physical activity in line with efforts to reduce smoking behavior.”
However, getting less than one hour of light activity per week had no effect on mortality in this study, again highlighting the importance of getting the “dosage” right if you want to live longer.
The Optimal Amount of Exercise for Longevity
Other recent research reveals that indeed there is a “Goldilocks zone” in which exercise creates the greatest benefit for health and longevity. In one study,11 data was collected from health surveys involving 661,000 adults and 14 years’ worth of death records.
Exercise habits ranged from no exercise at all, to 10 times the recommended amount (25 hours per week and over). Not surprisingly, those who did not exercise had the highest risk of premature death.
Those who met current recommendations of 150 minutes per week of moderate exercise lowered their risk of death by 31 percent compared to those who did not exercise, but it was those who tripled the recommended amount of exercise that gained the greatest benefits.
Exercising at moderate intensity for 450 minutes per week (just over an hour a day), lowered their risk of premature death by 39 percent, compared to non-exercisers. Beyond that, the benefits actually began to evaporate, and those who exercised at 10 times above the recommended level had the same mortality risk reduction as those who met the guidelines of 150 minutes per week (31 percent).
A second study,12 which focused on intensity, found that those who spent 30 percent of their exercise time doing more strenuous activities gained an extra 13 percent reduction in early mortality, compared to those who exercised moderately all the time and never really picked up the pace.
Inactivity Promotes Brittle Bones
Another benefit of exercise that becomes increasingly important with age is its impact on your bones. Recent research13 suggests that as mobility decreased over time, modern humans developed increasingly lighter, more brittle bones. As reported by Times of India:14
“The study of the bones of hundreds of humans who lived during the past 33,000 years in Europe sheds light on a monumental change that has left modern humans susceptible to osteoporosis, a condition marked by brittle and thinning bones.If you want strong, healthy bones, weight-bearing exercises like strength training should be a regular part of your fitness routine. Bone-building is a dynamic process, and you need to exert enough force on your bones to stimulate the osteoblasts to build new bone.
At the root of the finding is the knowledge that putting bones under the ‘stress’ of walking, lifting and running leads them to pack on more calcium and grow stronger... ‘By analyzing many arm and leg bone samples from throughout that time span, we found that European humans' bones grew weaker gradually as they developed and adopted agriculture and settled down to a more sedentary lifestyle,’ said Christopher Ruff from the Johns Hopkins University's school of medicine.”
Further, bone is living tissue that requires regular physical activity in order to renew and rebuild itself, so exercise needs to be a lifelong commitment. As you build more muscle, and make the muscle that you already have stronger, you automatically put more constant pressure on your bones. A good weight-bearing exercise to incorporate into your routine (depending on your current level of fitness, of course) is a walking lunge, as it helps build bone density in your hips, even without any additional weights.
Sitting Is the New Smoking...
The health effects of living too sedentary a life go far beyond reductions in bone density, however. I, for one, am absolutely convinced that sitting is in and of itself a root problem of many of our chronic health problems, and mounting research supports this notion. According to Dr. James Levine, co-director of the Mayo Clinic and the Arizona State University Obesity Initiative, and author of the book Get Up! Why Your Chair Is Killing You and What You Can Do About It, some 10,000 publications have shown that sitting is harmful to your health, irrespective of other lifestyle habits, including an excellent exercise program.
In fact, one recent systematic review15,16 of 47 studies on sedentary behavior discovered that the time a person spends sitting each day produces detrimental effects that outweigh the benefits reaped from exercise. Chronic sitting was found to increase your risk of death from virtually all health problems, from type 2 diabetes and cardiovascular disease to cancer and all-cause mortality. For example, sitting for more than eight hours a day was associated with a 90 percent increased risk of type 2 diabetes.
Other research17 found that those who sit the most have a 50 percent greater risk of all-cause mortality—in fact, chronic sitting has a mortality rate similar to smoking,18 increasing your rate of lung cancer by more than 50 percent! Your risk for uterine and colon cancer also increases by 66 and 30 percent respectively. The reason for this increased cancer risk is thought to be linked to biochemical changes that occur when you sit, such as alterations in hormones, metabolic dysfunction, leptin dysfunction, and inflammation—all of which promote cancer. Your risk for anxiety and depression also rises right along with hours spent in your chair.
Part of the reason why all of this may seem so surprising is that we've become so accustomed to sitting in chairs that we've failed to realize that doing so might be seriously problematic. Even I am perplexed at how I missed such a profoundly important health principle for the first 60 years of my life, but now that I have a better understanding of the science behind it, the cause and effect are quite clear. And so is the remedy.
Exercise Boosts Youthfulness, Even with Advancing Age
In short, exercise is one of the “golden tickets” to preventing disease and slowing the aging process. Besides helping you regain your insulin and leptin sensitivity, which is the root of most chronic disease, if you make the wise decision to engage in some intense exercise19,20 a couple of times a week, you’ll also boost your body's natural production of human growth hormone (HGH)—a biochemical often referred to as “the fitness hormone” for its invigorating, age-defying effects. It not only promotes muscle growth and effectively burns excessive fat; it also plays an important part in promoting longevity.
Once you hit the age of 30, you enter what's called "somatopause," at which point your levels of HGH begin to drop off quite dramatically. This decline of HGH is part of what drives your aging process, so maintaining your HGH levels gets increasingly important with age.
Besides that, exercise also induces changes in mitochondrial enzyme content and activity, which increases cellular energy production and triggers mitochondrial biogenesis21,22 (the process by which new mitochondria are formed in your cells). This reverses significant age-associated declines in mitochondrial mass, and in effect, “stops aging in its tracks.” Men will also be pleased to know that high-intensity interval training (HIIT), specifically, also helps boost testosterone levels naturally. That’s unlike aerobics or prolonged moderate exercise, which has been shown to have virtually no effect on testosterone levels.
Exercise Is Great Preventive Medicine
No matter what your age, exercise can provide enormous benefits for your health, and if you’re over 40, it's especially important to either start or step up your exercise program. This is the time of life when your physical strength, stamina, balance, and flexibility start to decline, and exercise can help to counteract most age-related decline. For tips on getting started, check out my fitness page, Mercola Peak Fitness, which is a treasure trove of fitness videos and articles related to exercise.
Ideally, establish a comprehensive exercise program that includes high-intensity exercises, strength training, core exercises, and stretching. I also urge you to consider walking more, in addition to your regular workout regimen. Ideally, aim for 7,000 to 10,000 steps per day. Also avoid sitting as much as possible—ideally limiting your sitting to three hours a day or less, as prolonged sitting is an independent risk factor for chronic disease and early death—even if you’re very fit and exercise regularly.
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