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How Much Physical Activity is Enough? Do We Really Know?

May 6, 2011



By Sheri Colberg, PhD


The physical activity debate is raging. How much activity should you do each day? How hard do you have to work out? Is walking enough? Can you get fit and lose weight simply by moving more? How much activity is enough?


Let’s start at the beginning of the debate. It has been firmly established that a sedentary lifestyle is not good for your health, period. Few people question that premise. Physical inactivity leads to lower fitness levels (which are linked to higher mortality rates) and greater muscle mass loss with aging, which increases the risk for metabolic disorders like Type 2 diabetes, sarcopenic obesity, and frailty. Being inactive also contributes to excessive weight gain over time because fewer calories are being expended each day. 

Breaking up sedentary time with any physical activity helps reduce the negative impact of being inactive, although to what degree remains to be determined. For example, a study by Bankoski and colleagues in the February 2011 issue of Diabetes examined 1,367 men and women 60 years or older who wore accelerometers to measure their sedentary time during waking hours. A sedentary bout was defined as a period of time >5 min where subjects recorded <100 counts per minute on the devices, while a sedentary break was defined as an interruption in sedentary time (≥ 100 counts per minute). On average, the participants spent 9.5 hours a day, or 65% of wear time, doing sedentary things. Those individuals with a higher percentage of sedentary time and fewer sedentary breaks had a greater likelihood of having metabolic syndrome. So, the amount of sedentary time in that study was strongly related to metabolic risk, independent of physical activity, which suggests that older people (and likely others) may benefit from reducing total sedentary time and simply avoiding prolonged periods of sedentary time by increasing the number of breaks during sedentary time.  

While we all like our modern conveniences, it is becoming increasingly obvious that most of them are not good for our health. In fact, the latest studies using human models of physical inactivity (e.g., bed rest, increased sitting time, and reduced daily ambulation) show that transitioning to physical inactivity rapidly reduced metabolic health. The technological advances that have removed our need to stand, walk, or move any limbs result in metabolic dysfunctions that likely play a fundamental role in the development of obesity and Type 2 diabetes — as well as other diseases that can shorten lifespan and reduce quality of life. 

By knowing that adding more physical movement to each day can benefit health, we have now circled back to the question of how much physical activity is enough. Many recent studies expound the cardiovascular virtues of undertaking more strenuous exercise like running or jogging compared to moderate activities like walking, but does that mean that you cannot gain any benefits from doing mild or moderate activities? 

The latest exercise guidelines from the U.S. government and from the American Diabetes Association agree that adults with and without Type 2 diabetes should strive to undertake at least 150 minutes of moderate-intensity aerobic activity per week, and the federal guidelines allow individuals to get by with 75 minutes of weekly vigorous activity (while the ADA sticks with 150 minutes of moderate-to-vigorous activity). 

But what happens if you get less than the recommended amounts of planned activity? And is it possible to benefit from unplanned movement throughout the day? The answer appears to be that any physical activity you get during the day — done at any intensity — can be beneficial to your overall health. While doing more vigorous activity (or at least faster intervals during a workout) can be beneficial, setting that up as a requirement when people are simply not moving enough now is daunting and best reserved for a long-term goal when the short-term ones involving more daily physical movement are met first. 

Finally, in reviewing what causes people to start and then stop exercise programs, keep in mind that any injury resulting from physical activity is likely to result in greater sedentary time and that exercise that is too hard (to start) is both demotivating and injury-provoking. It is far better to view a physically active lifestyle as a lifelong goal rather than a race to the finish line. Start out slowly, progress appropriately, and remove the usual barriers to sustained exercise participation by preventing injuries and exercise burnout.

In summary, there remains no doubt that the following are true:

  • It is unhealthy to be physically inactive.
  • Doing some activity, regardless of the intensity or duration, is better than doing none.
  • Many different levels of physical activity are likely beneficial, with the people with the lowest fitness levels (i.e., going from sedentary to any level of activity) gaining the most health benefit.
  • It’s never too late to start getting more active, even if that just means standing more and taking more daily steps to start.

Sign up for the newly-launched DIABETES "Fit Brain, Fit Body!" fitness/lifestyle programs or for 5 free Healthy Living Reports at www.lifelongexercise.com, and access more articles and information at www.shericolberg.com. If you need tips for getting safely started on an exercise program, check out The 7 Step Diabetes Fitness Plan. For people with any type of diabetes who are already more active, consult the Diabetic Athlete’s Handbook.

Click here for a full list of all of Sheri Colberg’s articles on fitness and diabetes.

Copyright © 2011 Diabetes In Control, Inc., www.DiabetesInControl.com