Comments on OBESITY PANACEA: Too Much TV Reduces the Benefits of Physical Activ...

@ Anonymous, You are absolutely correct that fitn...

2010-01-13T23:00:13.912-05:00

@ Anonymous,

You are absolutely correct that fitness and physical activity are two different things, although they obviously interact. Which one you use really depends on the question that you want to ask. Physical activity is a behaviour which is largely (but not exclusively) under the control of the individual, but fitness is an outcome which depends not only on physical activity, but also on genetic factors. For that reason I am personally more interested in physical activity, since it has a more relevant public health message (better to focus on something that people can more easily change).

It's not necessarily that TV time offsets the calories that you would expend during your run. When you sit for an extended period of time, it affects the lipoprotein lipase activity in your muscles, which results in increased blood fat, and reduced HDL (good) cholesterol. These are both bad things, and surprisingly, this is NOT just the opposite of what happens when you exercise. This is probably why we are starting to see these strange interactions between TV time and physical activity. There is a terrific paper by Marc Hamilton that does a great job of examining how both exercise and sedentary time affect metabolic health.

Travis

It has been shown that physical activity and actua...

2010-01-13T13:05:35.623-05:00

It has been shown that physical activity and actual fitness are too different things. People who are physically fit have a stronger inverse relation with heart disease risk http://healthresearch.lbl.gov/vs.html
Perhaps this research would be better using a treadmill test to determine fitness rather than reported hours of activity. I run on average about 50 minutes per day, about 35 miles per week, my BMI is about 22.8. I currently sit at a desk for most of my workday (except during my lunch when I run). I calculated last week that I burned over 5,000 calories running (43.5 miles). It is hard to believe that an hour in front of the TV is negatively equal to my 5,0000 calories, unless every time I sit in front of the TV for an hour, I consume over 1,000 calories in snack foods.

@ Gina, Research like this actually scares me a b...

2009-12-16T22:09:37.824-05:00

@ Gina,

Research like this actually scares me a bit, as I tend to fall into the category of the person who does a solid workout, followed by several hours of sitting at a computer. I bike to work most of the year, and take frequent breaks to stretch my legs, so it's not like I'm completely sedentary during the workday, but I do start to wonder how my life as a desk jockey impacts my longterm health :)

Thanks for this informative post, Travis. So what ...

2009-12-16T21:45:25.583-05:00

Thanks for this informative post, Travis. So what you're saying is that even if I'm watching The Biggest Loser, I'm probably becoming The Bigger Watcher?? Darn! Here I was thinking that it was totally OK to surf the couch guilt-free after my daily workout. Go on, keep raining on my parade. (great post though, seriously)

@ Anonymous, Great questions. In general, sedent...

2009-12-16T20:06:47.743-05:00

@ Anonymous,

Great questions. In general, sedentary behaviours are bad. For example, studies that measure total sedentary time by having people wear pedometers find that it is strongly associated with things like obesity and chronic disease risk. TV appears to be even worse than some other sedentary behaviours though, because it is often accompanied by snacking on high fat foods as Caroline suggested, and also tends to expose people to advertisements for "bad" foods. There is even some research suggesting that we burn less calories when watching TV than during other sedentary behaviours.

One of the most famous studies on physical activity actually looked at the heart disease risk of bus drivers (who spend most of the day sitting) and ticket takers (who spend most of the day walking up and down the aisle) in the middle part of the 20th century. Just as you'd expect, those who walked more had dramatically lower health risk than those who spent the day sitting down. I don't have a link off hand, but it's one of the first papers to really show that physical activity has health benefits. It may turn out that we have simply underestimated the negative impact of being sedentary all day long. If anyone has a link to the study I am referring to, please feel free to post it below.

Travis

You mention that too much sedentary time, in parti...

2009-12-16T19:21:53.260-05:00

You mention that too much sedentary time, in particular TV watching time, is a risk factor for disease and mortality. What about other sedentary activities... e.g. people using computers, people with office jobs, etc. Also, are there studies on occupation-related obesity risk?

Great article Travis! Good reminder to take advan...

2009-12-16T17:26:40.203-05:00

Great article Travis!

Good reminder to take advantage of the free time during the holidays to add more activity to my day!

@ Caroline, That's a great point, and there a...

2009-12-16T15:41:32.278-05:00

@ Caroline,

That's a great point, and there are a few interventions that suggest you may be right (I'm hoping to discuss them in the near future). In the meantime, you might want to check out this recent paper by Gary Goldfield and colleagues.

There are also some cool studies suggesting that sitting actually has very specific and rapid effects on muscle metabolism, which are likely to also play a role in the links between sedentary behaviours and obesity/disease. There is a great paper on the topic by Lionel Bey, and it can be found here.

Travis

I found this quite an interesting read. The one th...

2009-12-16T15:30:40.063-05:00

I found this quite an interesting read. The one thing that came to mind while reading this was the fact that it may not be the actual sitting that increases mortality risk, but rather what might be done while sitting (i.e. mindless eating). I'm guessing they didn't measure that in the study, did they?

For clarification, it is increased risk of death i...

2009-12-16T13:37:03.844-05:00

For clarification, it is increased risk of death in a finite period (12 years in this case).

:)

Travis

"...too much time sitting down is a risk fact...

2009-12-16T13:28:19.507-05:00

"...too much time sitting down is a risk factor for obesity, chronic disease, and even death..."

I'm fairly certain that everyone's risk (and, indeed, experience) of death is 100%, even if they've never seen a TV.