How Physical Inactivity Increases Risk for Chronic Diseases

December 23, 2016 | 125,083 views


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By Dr. Mercola

Evidence shows that inactivity or lack of movement that is best exemplified by prolonged sitting, actively promotes dozens of chronic diseases, and these risks apply even if you're very fit.1,2 In fact, sitting for too long, too often, is an independent risk factor for ill health and reduced longevity.

Dr. James Levine is 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."

According to Levine, there are at least 10,000 published studies showing that sitting harms health, irrespective of other lifestyle habits, including an excellent exercise program.

Your Risk for Chronic Diseases Skyrocket If You're Inactive

An interactive body map published by The Conversation allows you to select a body part and/or disease to see the scientific support linking any given health problem and inactivity.3,4

For example, physical inactivity raises your risk of general ill health by 114 percent, your risk of Alzheimer's disease by 82 percent and your risk of depression by 150 percent.

Overall, chronic sitting has a mortality rate similar to smoking.5 It even increases your chances of lung cancer by more than 50 percent. Your risk for uterine and colon cancer also increases by 66 and 30 percent respectively.

Fortunately, the remedy is simple: Avoid sitting and get more movement into your life. As the dangers of inactivity have become more widely recognized, a number of excellent books have been published on the subject. One of my favorites is Kelly Starrett's book, "Deskbound: Standing Up to a Sitting World."

It's filled with helpful guidance that can improve your health and well-being, covering both tips to naturally increase your daily movement and proper body mechanics. It is one of the best books I read this year and I believe it's an important resource for anyone that has a sitting job.


AWhy Sitting Causes so Much Harm

Inactivity affects your health in a number of different ways, but one foundational mechanism of harm relates to the molecular cascades that occur simply by standing. Within 90 seconds of standing up, your muscular and cellular systems that process blood sugar, triglycerides and cholesterol are activated.

Most of these systems are influenced by insulin. As you probably know, one of the primary benefits of exercise is improved insulin receptor sensitivity, thus lowering insulin resistance. But even the act of standing (as opposed to sitting) will have a beneficial effect.

On the other hand, sitting for more than eight hours a day has been shown to increase your risk of type 2 diabetes by 90 percent.6

Essentially, what science tells us is that, at the molecular level, your body was designed to be active pretty much all day long and regularly neglecting this requirement will result in health challenges.  

Sitting impairs these molecular events that are necessary for optimal biological functioning, thereby setting the stage for disease. In other words, while we certainly need to rest from time to time, that rest is supposed to break up activity, not the other way around.

Inactivity simply isn't supposed to be a way of life, as excessive sitting switches off the natural fueling systems in your body and down-regulates your metabolism. As a consequence of sitting, blood sugar, blood pressure and cholesterol imbalances arise.

The modern sitting posture is also very bad for your back, neck, wrists and arms, leading to a variety of chronic pains. Pills are not the solution for any of these problems. The real answer is to get up and avoid sitting as much as possible. As a basic guideline, if you've been sitting down for a full hour, you've sat too long.

The Biological Imperative of Movement

Research looking for clues about people's natural movement patterns reveals there appears to be "biological imperatives to movement" built into our system.

One such study7 found that not only do people tend to move and rest in logical intervals, physical activity also appears to affect your body's internal clock mechanisms and circadian rhythms.

The intervals of movement and inactivity were more consistent in younger people than older ones. As noted in the featured article:8

"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.

In doing so, the researchers felt, the body created a healthy, dynamic circadian pattern."

Another study,9 this one looking at the movement of mice, also concluded that exercise plays a role in maintaining a healthy circadian rhythm, allowing the animals to maintain more natural activity patterns. Without exercise, the animals' activity levels became more random. According to The New York Times:10

"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."

Diabetes, Heart Disease and Cancer Are All Related to Inactivity

Diabetes, cancer, heart and neurodegenerative diseases are the most common diseases in the developing world, especially the U.S., and all are significantly influenced by your level of physical activity.

Starting with diabetes, I just described the metabolic consequences of sitting versus standing. Diabetes in turn raises your risk of both heart disease and cancer (plus many others, including dementia), so by reducing your risk of diabetes you automatically raise your protection against other chronic diseases as well.

Globally, cardiovascular disease (CVD) accounts for 38 percent of all deaths, and rates are rising even in developed nations where the condition has historically been low, in large part due to a more natural diet and higher physical activity levels.

According to a recent investigation, over 78 percent of Nigerians now live a sedentary lifestyle and 30 percent have high blood pressure. According to Dr. Casmir Amadi, a senior consultant cardiologist at the Lagos University Teaching Hospital in Nigeria, these health effects are the result of urbanization and increased use of motorized vehicles.11

Villagers who still walk long distances on a daily or near-daily basis do not have the same high rates of disease as city dwellers. Even children are starting to experience the adverse effects of modernization and the proliferation of junk food. As noted by Amadi, who urges all Nigerians to exercise daily:

"Once a child gets exposed to junk food early enough in their life, the chances [are] that they will get bigger and once they become obese, they can start having diabetes very early in life, and diabetes and obesity are all CVD risk factors."

An Active Lifestyle 'Insulates' You From Cancer

Many studies have also highlighted the role of physical activity in both the prevention and treatment of cancer. Again, one of the primary mechanisms responsible for driving down your cancer risk is the fact that exercise decreases your insulin resistance. By creating a low sugar environment in your body, the growth and spread of cancer cells are significantly discouraged.

Movement also improves circulation, driving more oxygen into your tissues and circulating immune cells in your blood. According to a 2003 paper,12 more than 100 epidemiologic studies looking at the impact of physical activity on cancer prevention reveal that:

"[P]hysically active men and women have about a 30 to 40 percent reduction in the risk of developing colon cancer, compared with inactive persons … With regard to breast cancer, there is reasonably clear evidence that physically active women have about a 20 to 30 percent reduction in risk, compared with inactive women."

This pattern of a 20 to 40 percent risk reduction appears again and again in studies looking at the effects of exercise on cancer, although some show even higher rates of protection. A small sampling of such studies includes the following:

•A recent Danish study, which followed more than 5,130 middle-aged men for 44 years, found that the better a man's respiratory fitness, the less likely he is to die from cancer. More specifically, for every 10 mL/kg/min increase in VO2 Max at baseline (around the age of 49), the risk of dying from cancer was reduced by 17 percent, and the risk of dying from any cause in the next 40+ years was reduced by 11 percent.13,14

•Being fit in middle age also cut men's risk of being diagnosed with lung cancer by 55 percent and bowel cancer by 44 percent, and reduced the risk of dying from lung-, bowel- and prostate cancer (if they did get it) by 32 percent.15,16

•Animal research suggests regular exercise may be the key to significantly reduce your chances of developing liver cancer, which is among the most common types of cancer.17,18

•Breast- and colon cancer patients who exercise regularly have half the recurrence rate as non-exercisers.19

Weight training cut men's risk of dying from cancer by 40 percent, and similar findings have been reported in other studies involving both men and women.

Exercise Helps Protect Your Neurological Health Too

Exercise also helps protect your neurological function. In fact, it may be part and parcel of staying "sharp as a tack" well into old age. As with the rest of your body, a number of mechanisms are at play. For example, research shows that exercise:

Increases blood flow to your brain, which allows it to almost immediately function better. It also promotes genetic changes. The increased blood flow adapts your brain to turn different genes on or off, and many of these changes help protect against diseases such as Alzheimer's and Parkinson's.

Promotes growth of new brain cells. In your hippocampus, these new brain cells help boost memory and learning.20

Helps preserve both gray and white matter in your brain, which prevents cognitive deterioration that can occur with age.21,22

Triggers the release of neurotransmitters, including endorphins, serotonin, dopamine, glutamate and GABA. Some of these are well-known for their role in mood control. Not surprisingly, exercise is one of the most effective prevention- and treatment strategies for depression.

Increases brain derived neurotrophic factor (BDNF). Exercise stimulates the production of a protein called FNDC5 that then triggers the production of BDNF, which has remarkable rejuvenating abilities. In your brain, BDNF both preserves existing brain cells,23 and activates brain stem cells to convert into new neurons, effectively making your brain grow larger.24

Decreases BMP and boosts Noggin: Bone-morphogenetic protein (BMP) slows down the creation of new neurons, thereby reducing neurogenesis. If you have high levels of BMP, your brain slows and grows less nimble. Exercise reduces the impact of BMP, allowing your adult stem cells to continue performing their vital functions of keeping your brain agile.

In animal research, mice with access to running wheels reduced the BMP in their brains by half in just one week.25,26 In addition, they also had a notable increase in another brain protein called Noggin, which acts as a BMP antagonist.

So, exercise not only reduces the detrimental effects of BMP, it simultaneously boosts the more beneficial Noggin as well. This complex interplay between BMP and Noggin appears to be yet another powerful factor that helps ensure the proliferation and youthfulness of your neurons.

Reduces plaque formation: By altering the way damaging proteins reside inside your brain, exercise may help slow the development of Alzheimer's disease.27

Regular Movement Is Critical for Optimal Health

The average American adult spends about 10 hours or more each day sitting, and research shows you simply cannot offset 10 hours of stillness with one hour of exercise. You ideally require near-continuous movement throughout the day, even if it's just standing rather than sitting. So, strive to sit for less than three hours a day, and make it a point to walk more.

A stand-up desk is a great option. But even then you should move, not just stand, as lack of movement, not just sitting, is the primary catalyst for metabolic dysfunction. A fitness tracker or smartphone can be used to ensure you're getting the recommended 7,000 to 10,000 steps per day, but that doesn't mean you stop at 10,000 steps. When you have time you can go for walks twice as long.

Next you'll want to incorporate a more regimented fitness routine, and while virtually any exercise is better than none, high-intensity exercises are the most potent. Benefits of high-intensity interval training (HIIT) include cardiovascular fitness, improved muscle growth and strength and the generation of "anti-aging" human growth hormone (HGH), also referred to as "the fitness hormone."

It also effectively stimulates your muscles to release anti-inflammatory myokines, which increase your insulin sensitivity and glucose use inside your muscles. They also increase liberation of fat from adipose cells, and the burning of the fat within the skeletal muscle.

Strength training is another important component, as are mobility therapies such as those described by Starrett in his book, "Deskbound." A foam roller is an inexpensive fitness tool that can be quite useful for this. Whatever you choose to do, please do take the time to exercise, and be sure to incorporate as much physical activity into your life as you can on an hourly basis.