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Wednesday
Oct262011

The Metabolic Effects of Your Sedentary Lifestyle

If you’re like most people, you probably believe you live an active lifestyle. In fact, when surveyed, 65% of the population claimed to live an active lifestyle. However, when people’s level of activity is actually measured, research shows only 5% of the population is living an active lifestyle![i]

For perspective, I generally workout five days per week. I spend much of my day at my desk on the computer or running to meetings. Our meetings are usually in a conference room, so I get up frequently. For several weeks, I wore an accelerometer which identified how much of my day I was being “active.” The numbers were not impressive. On workout days, I averaged 75 minutes of activity. On days I didn't exercise, I averaged 15 minutes of activity a day! Think about that – I was active for 75 minutes at most on a given day! We may be busy, we may have a lot of activities we’re involved in, but in terms of movement, 95% of us are not active.  According to a new study in The Journal of Applied Physiology, our sedentary lifestyle results in a lot more than poor posture and a loss of the physical performance we had when were young.

A small group of researchers reviewed existing data on the impact of bed rest on the body’s metabolism. How does bed rest relate to being sedentary? In terms of activity, our bodies are not faced with much more activity when we’re sedentary than those stuck in bed. Therefore, much of what the researchers found could be related to sedentary lifestyles as well.

Metabolic Flexibility

Getting back to the study, the research group looked at how being sedentary affects the body’s metabolic flexibility, a term used to describe how well the body can shift from using carbohydrates for fuel to fat.[ii] A healthy metabolism favors the use of fat for fuel while at rest, and even during most types of exercise. Poor metabolic flexibility results in

  • Insulin resistance, or the loss of ability to properly use insulin and a rise in fasting blood sugar
  • Reduced ability to mobilize fat stores and an increase in fat in the blood
  • Increased reliance on carbohydrate, or glucose for fuel
  • Reduction in the muscle tissue type that burns fat along with an increase in fat tissue
  • The research looked at how being inactive affects metabolic flexibility.

Insulin Resistance

Insulin resistance is an early step in the direction toward type II diabetes. When the body becomes inactive, muscle tissue loses its ability to move incoming carbohydrate, or glucose, from the blood into the muscle. Since blood sugar levels remain higher than they should, the pancreas secretes more insulin to get the glucose into the muscle. At the same time, the body will take some of this extra sugar and convert it to fat. Add poor dietary choices like cereal and juice for breakfast or a sandwich and chips for lunch, and the excessive carbohydrates make the problem even worse. While insulin is elevated, the fat cells won’t break down and release fat for energy, so the body shifts to using more carbohydrate for fuel.

We often see evidence of developing insulin resistance when people have their resting metabolic rate assessment, or CaloriePoint done. Those who don’t burn fat well have a higher respiratory quotient (RQ), which is an indicator of how well they burn fat. The measure is from 0.7 to 1.0 and is related to the ratio of oxygen inspired to carbohydrate expired.  The closer one is to 1.0, higher the percentage of carbohydrate they burn, a sign of an inefficient metabolism.

What’s more, the researchers also found that even when people were eating a low-calorie diet, the fact that they were sedentary still induced insulin resistance. If an individual is on a reduced-calorie diet, trying to lose weight, but can’t use fat for fuel because they are resistant to insulin, they may find any weight loss they achieve will come from muscle rather than fat. They might lose some weight, but they won’t be any leaner.

Even more fascinating is the fact that most of the research was done on healthy individuals, without a history of insulin resistance or diabetes. If healthy individuals are affected this much, imagine how much worse it could be for those already displaying signs of insulin resistance or blood sugar issues, such as those who are overweight or have type II diabetes.

Fat mobilization

As mentioned above, being sedentary increases insulin levels which, in effect, “locks up” fat in the fat cells. It can’t be burned when insulin is elevated. Even though fat is not released from the fat cells into the blood, sedentary people show an increased amount of fat, or triglycerides, in the blood. Since the fat isn’t coming from the fat cells, it is likely coming from the diet. Incoming carbohydrate, as we discussed above, is not allowed to enter the muscle tissue, so it gets converted to fat at an increased rate, pushing up triglyceride levels.

Being sedentary causes  muscle to lose its mitochondria, the power houses of the cell, where fat is burned. Less mitochondria, less ability to burn fat. The body continues to burn glucose, store more fat and decrease the amount of muscle it has. In essence, lipid levels in the blood continue to increase

Another interesting finding was the fact that inactivity contributes to an increased number of fat cells, rather than an increased size of current fat cells.

Fat accumulation and muscle loss

With a reduced ability to burn fat and an increase in the signals to store fat, you can imagine sedentary lifestyles result in more overall fat stores. The fat gain can take place even while following a low-calorie diet. Fat gain from being sedentary results in “general” fat gain. This is different than the way high stress levels and fructose tend to increase visceral (belly) fat, or high estrogen increases fat tissue in the chest (especially in men), triceps and thighs, which is more “specific” fat gain. Instead, being sedentary seems to increase fat storage throughout the body – between muscle cells, in the bone marrow and even contributing to nonalcoholic fatty liver. With a higher level of fat in the blood, there is a greater chance of developing high levels of oxidized LDL cholesterol or the really bad cholesterol, very-low density lipoprotein (VLDL).

Though it was not discussed in this research paper, it’s quite plausible that becoming inactive also results in a process called transdifferentiation. Transdifferentiation is a process by which some of the cells of the body can change roles. As Catherine Shanahan describes in her book Deep Nutrition, “muscle cells can become fat cells; fat cells can become bone; and then a bone cell can change back to a fat cell again.”[iii] These cells change their form based on the stimulus they get from the rest of your body. If you’re not using muscle, why keep it muscle? Think about that as you consider the current level of activity you get each week. Are you giving your body the signals it needs to build a healthy, functioning system? If not, the logical alternative is to make more fat.

Summary

Activity and exercise are not always the same. You may be making time for a workout each day, but what are you doing the other 15 hours you’re awake? If most of the rest of your time is spent sitting down, think about the effect it may be having on your health. Find time during the day for an extra walk. Make it a point to get up and move around as often as possible. At night, do something active for half an hour before you sit down. There’s nothing more important than your health, and your health is directly related to the flexibility of your metabolism.

Keep the discussion going below.

Written by Tom Nikkola – Director of Nutrition & Weight Management

This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.


[i] Troiano RP, Berrigan D, Dodd KW, Masse LC, Tilert T, McDowell M. Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc 40: 181–188, 2008.

[ii] Bergouignan A, Rudwill F, Simon C, Blanc S. Physical inactivity as the culprit of metabolic inflexibility: evidence from bed-rest studies. J Appl Physiol. 2011;111:1201-1210

[iii] Shanahan MD, Catherine (2011-04-22). Deep Nutrition: Why Your Genes Need Traditional Food (Kindle Locations 3764-3769). Big Box Books. Kindle Edition

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Reader Comments (1)

Great article Tom.....As a Team Weight Loss Instructor in San Antonio I am constantly expressing the importance of 'daily movement' to my classes. Coming in the the gym to do 60 minutes of Heart Rate Zone based fat burn training 3 times a week is awesome and a great way to get started. Increasing your 'daily movement' with non specific activity can help increase the total calories your body burns everyday. When you combine that additional movement with a Nutrition plan that stabilizes your Blood Sugar, you are set up for success!! Good Luck increasing your amount of Daily Movement.
Cheers,
Simon 'Wallaby' Toozoff

October 31, 2011 | Unregistered CommenterWallaby

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