The Truth About “The Truth About Sitting Down”

Image from Wired

After hearing about the benefits of standing desks for a while now, I finally sorted out a standing desk at work last month. It’s just an old desk I found, balanced on top of my original desk, but it puts my keyboard at a perfect height. I have to say, I don’t miss sitting at all. At the end of a long day in front of my computer, my feet hurt much less than my back used to. The only down side is that I tend to look a bit ridiculous when I’m working with headphones on and find myself dancing in place at my desk.

Being an empirical scientist, I know I can’t always trust my own perceptions about the benefits of an intervention. Any sort of change can increase productivity, so I’ve been looking for scientific evidence for the benefits of standing desks. An infographic, Sitting Down is Killing You by MedicalBillingandCoding.org, portrayed the state of research being strongly in favour of standing desks, but how accurate are the claims?

This infographic is much better than most because it includes references in a list at the end of the image, but each specific claim isn’t cited, so I looked up all 12 links to find the evidence behind the pictures (see the list at the end of this article). Let’s take a closer look at a few of the stats.

Sitting Increases Risk of Death Up to 40%?

The first major statistic on the infographic is this:

Sitting 6+ hours per day makes you up to 40% likelier to die within 15 years than someone who sits less than 3. Even if you exercise.

I tracked this claim down to an article in The New York Times, which states:

Alpa Patel, an epidemiologist at the American Cancer Society, tracked the health of 123,000 Americans between 1992 and 2006. The men in the study who spent six hours or more per day of their leisure time sitting had an overall death rate that was about 20 percent higher than the men who sat for three hours or less. The death rate for women who sat for more than six hours a day was about 40 percent higher.

Even from this brief description of the study, you can tell that this statistic is misleading as written. The increase in death rate for men was half this figure, but the infographic gives no hint of a sex difference.

Reading the actual study in the American Journal of Epidemiology provides further clarification. The participants in this study were healthy adults age 50–74 at the beginning of the study, so it’s unclear how the results apply to younger adults.

Additionally, the study only measured non-working sitting time. The exact question was, “During the past year, on an average day (not counting time spent at your job), how many hours per day did you spend sitting (watching television, reading, etc.)?” However, the same panel includes a pie graph that states the average person is sedentary 9.3 hours per day, implying that the dangerous level of 6+ hours of sitting per day is epidemic and includes sitting at work. In actuality, only 9% of women and 13% of men in this study sat for more than 6 hours per day, compared to 49% of women and 43% of men who sat for less than 3 hours per day outside of work.

How Sitting Wrecks Your Body?

The claims made in this panel set off my skeptic alarm immediately. The infographic claims that:

As soon as you sit:

• Electric activity in the leg muscles shuts off
• Calorie burning drops to 1 per minute
• Enzymes that help break down fat drop 90%

After 2 hours: Good cholesterol drops 20%

After 24 hours: Insulin effectiveness drops 24% and risk of diabetes rises

I traced two of these claims to an article in Business Week. The article contains the uncited statements:

When you sit, the muscles are relaxed, and enzyme activity drops by 90% to 95%, leaving fat to camp out in the bloodstream. Within a couple hours of sitting, healthy cholesterol plummets by 20%.

The other claims come from an article in the New York Times that quotes and paraphrases Marc Hamilton from the Pennington Biomedical Research Center:

This is your body on chairs: Electrical activity in the muscles drops — “the muscles go as silent as those of a dead horse,” Hamilton says — leading to a cascade of harmful metabolic effects. Your calorie-burning rate immediately plunges to about one per minute, a third of what it would be if you got up and walked. Insulin effectiveness drops within a single day, and the risk of developing Type 2 diabetes rises. So does the risk of being obese. The enzymes responsible for breaking down lipids and triglycerides — for “vacuuming up fat out of the bloodstream,” as Hamilton puts it — plunge, which in turn causes the levels of good (HDL) cholesterol to fall.

So it looks like most of these claims are potentially supported by the evidence, even though they are presented in a fairly sensationalist manner. For instance, the claim that electrical activity in the leg muscles shuts off as soon as you sit down is fully supported by evidence in this graph, but it isn’t at all clear how this statistic relates to general health, as electrical activity normally “shuts off” in any muscle when it isn’t being used.

Standing Desks in the News

While the infographic overstates and mischaracterises some of the evidence (not unusual for infographics), the general conclusion holds true even after a closer look at the sources. There is a huge amount of quality reporting on research on the benefits of standing desks, including several of the links cited in the infographic (and below).

More recently, the BBC, in collaboration with researchers at the University of Chester, published the results of a small study on the benefits of standing at work: Calorie burner: How much better is standing up than sitting? On the basis of data from 10 volunteers with normally sedentary jobs at an estate agents who stood for 3 or more hours per day, they concluded:

If you stand for three hours a day for five days that’s around 750 calories burnt. Over the course of a year it would add up to about 30,000 extra calories, or around 8lb of fat.

“If you want to put that into activity levels,” Dr Buckley says, “then that would be the equivalent of running about 10 marathons a year. Just by standing up three or four hours in your day at work.”

So I’ll be sticking with my standing desk. It’s certainly easier than a marathon!