J Leonard Dixon

Earlier in Chapter 12 I discussed the systematic analysis of 232 studies with almost 1 million children performed by Tremblay and colleagues. The authors stated,

“Qualitative analysis of all studies revealed a dose-response relation between increased sedentary behaviour and unfavourable health outcomes. Watching TV for more than 2 hours per day was associated with unfavourable body composition, decreased fitness, lowered scores for self-esteem and pro-social behaviour and decreased academic achievement.”

The authors also indicated that the above negative changes could be reversed if children watched less than 2 hours of television per day.

Mark S Tremblay, Allana G LeBlanc, Michelle E Kho, Travis J Saunders, Richard Larouche, Rachel C Colley, Gary Goldfield and Sarah Connor Gorber. Systematic review of sedentary behaviour and health indicators in school-aged children and youth.

Online open access:   http://www.ijbnpa.org/content/8/1/98

I repeat the above observations because it is interesting that the two-hour time point seems to be an important time mark for causing physiological changes in children. But what is just as interesting is that the two to 2.5 hour time point appears to be important in causing physiological changes in adults, too.

In my nutrition and health class, students always ask about the role of structured exercise (done in a gym or at home on a treadmill, etc.) in treating obesity. I let them figure it out for themselves. I give them an assignment where they calculate their daily energy expenditure and I have them list their favorite activities/exercise and list the kilocalories (kcal) expended per hour during each activity. Then I have the students list their favorite snacks with the kcal each one has. The reaction to this assignment has been consistent every year for the past ten years: “I can’t believe how long I need to exercise to burn off the kcal in my favorite snack!” It is just too easy in today’s environment to eat excess kcal! The take home message from this assignment is that structured exercise is not a way to treat or prevent obesity, unless you have enormous amounts of time to spend in the gym (say 3-4 hours per day). I haven’t met anybody with that kind of time yet!

What I teach in my class is that structured exercise is important and necessary for the following reasons:

1) keep coronary artery smooth muscle cells healthy so that they can dilate when your heart is called upon to pump extra blood;

2) keep ligaments and connective tissue strong and flexible so that you do not have injuries;

3) put stress on your bones to keep them dense and strong, and

4) keep skeletal muscles from dissolving away with age.

But exercise is very important in helping us maintain a healthy body weight. Dr. James A. Levine of the Mayo Clinic has spent a good part of his career researching and promoting the role of Non-Exercise Activity Thermogenesis (NEAT) in influencing a person’s body weight.

What is NEAT? NEAT is the energy we expend each day in every day activities such as walking, standing, cleaning the house, taking public transportation to work, walking the dog, standing instead of sitting, taking the stairs, and playing with the kids. Dr. Levine has used state of the art measuring devices in his studies of people’s everyday activities, and he has determined that people who are able to maintain a healthy body weight expend approximately 2.5 hours more NEAT per day than people who have difficultly maintaining their weight.

Dr. Levine has commented, “Thus, the obesity epidemic may reflect the emergence of a chair-enticing environment to which those with an innate tendency to sit, did so, and became obese. To reverse obesity, we need to develop individual strategies to promote standing and ambulating time by 2.5 hours per day and also re-engineer our work, school, and home environments to render active living the option of choice.”

Levine JA, Vander Weg MW, Hill JO, Klesges RC. Non-exercise activity thermogenesis: the crouching tiger hidden dragon of societal weight gain. Arteriosclerosis, Thrombosis and Vascular Biology 2006: 26: 729-736.

http://atvb.ahajournals.org/content/26/4/729.long

Why is NEAT more helpful in maintaining weight than structured exercise? Because we do NEAT more often! This is shown in the following figure.

In the figure, several examples of energy expenditure are given for the same sized man. The blue-collar worker expends more energy per day than the worker who sits at a desk all day. Even adding 1 hour of swimming per day to the desk worker’s total energy expenditure does not bring the total kcal expended for the desk worker up to that expended by the blue-collar worker.

Most people who perform structured exercise regularly do so only about 4 hours per week or less. People who perform greater than average NEAT do so every day/7 days a week! On average, a person who expends a large amount of kcal in everyday activities will burn 500 more kcal per day than a person with a similar body type who does little NEAT per day. The reason for our lower levels of NEAT today are due to many reasons- jobs where we sit all day in front of a computer, no need to hand wash the clothes and hang them out to dry, driving to the supermarket instead of walking or having to hitch the horse to the buggy. The reasons are numerous because of all the work saving devices that have been introduced into modern day society. And then there was the introduction into the home of the two major digital systems in the late 1900s: cable TV, large screen televisions, VCRs, and the remote control devices that led to longer hours of inactivity, and easy to use and more powerful desk top computers that also nailed people’s rear ends to chairs.

Dr. James Levine, in a series of brilliant studies, documented the role of NEAT (i.e., the lack of it) in the obesity epidemic in the US. See his articles through the links below!

How do we increase NEAT in our everyday lives?

It’s easy but hard. By this I mean all we have to do is to reverse what we have done to decrease NEAT in the past 45 years. But giving up our digital devices and other work savers requires a conscious decision not to benefit from all of these modern conveniences. Here are some suggestions. The first thing is to throw out the television set. There is nothing that causes you to sit and not move more than watching television. If you do not wish to part with your TV, then an alternate would be to throw out the couch and replace it with a treadmill. However, most people do not use their treadmill no matter what! Another way to increase NEAT is to walk to work and/or use public transportation. This will provide 30 to 90 min per day of exercise depending upon your commute circumstances. If it is impossible to commute from where you live – move! And the act of moving will boost your activity level right there and then! Another way to increase NEAT is to get a job where you need to walk around. Again, you need to be committed in order to get that NEAT! If you do not want to change jobs, consider installing a treadmill desk in your office. In fact, there are directions on how to build your own treadmill desk on the Internet! And you can get exercise in the building process! There are numerous ways to increase NEAT in your life!

What is structured exercise good for? Is it important?

Yes, it is amazingly important because you still need the four health benefits that I wrote about earlier in this chapter. Most important, you need to perform 4 hours of strenuous exercise per week, in addition to the increased NEAT, to keep your heart muscles and coronary artery smooth muscle cells in good shape! Please see a few of the many publications by Dr. James Levine by clicking on the links below:

http://bjsm.bmj.com/content/41/9/558.long#global-tab-quality

http://www.hindawi.com/journals/jobe/2011/358205/