Sitting, Part 1: Myths and Truths about Sitting, Obesity, and Chronic Disease

A few years ago, everyone suddenly started lamenting the dangers of sitting. Sitting is associated with obesity, cancer, metabolic syndrome, cardiovascular problems, and early death.  (There’s also a lot of research on sitting and back pain, movement imbalances, and postural problems – that’s coming up in another article but it’s not addressed here. Here, it’s just about obesity and chronic diseases.) And that’s after controlling for exercise – running for an hour doesn’t absolve you from sitting all day.

On the other hand, moving around during the day is associated with health benefits: in this study, for example, people who spent more time on non-sedentary activities were less likely to have metabolic syndrome, obesity, and high cholesterol.

This got distilled into attention-grabbing headlines like “Sitting More Dangerous Than Cigarettes” or “Sitting Kills” – but as usual, shortening the topic for a sound bite came at the expense of accuracy.

First of all, not all studies show a direct connection between sitting and health problems. For example, this review looked at several different studies measuring connection between occupational sitting (that’s sitting at work) and obesity, cancer, cardiovascular disease, diabetes, or overall mortality. Sitting at work is the largest chunk of sitting in most people’s day, so it’s a good proxy for total sitting time. The authors concluded that there is no clear relationships: different studies all found different things.

If all those studies are finding such different results, it’s probably a sign that something more complicated than just “sitting” is going on. Specifically, it’s important to know what kind of sitting we’re talking about:

• Studies that just measure total sitting time may not control for the other unhealthy behaviors that go along with sitting. For example, sitting to watch TV often includes eating unhealthy snacks. So which is the problem, the sitting or the snacks?
• Many studies show the dangers of sitting for hours at a time without a break. Does this still apply to people who take brief but well-planned movement breaks during their “sitting time”?

So instead of just rehashing the “dangers of sitting” without any context, here’s a look at exactly what kind of sitting is dangerous:

Sitting vs. Sitting-Associated Behaviors

One big puzzle about sitting research is the difference between TV watching and other sitting.

TV watching specifically is consistently associated with health problems. But “sitting” in general, or sitting for other reasons, is not.

Sitting is sitting is sitting, so why does it matter if you’re sitting in front of a book or a TV? Sure, you could say that most people tend to have bad posture when they watch TV, but people also have terrible posture when they sit at work (hunched forward, back slumped). Posture can’t be the whole difference.

Instead, the difference seems to be all the other things that people do when they watch TV. Specifically, it’s the fact that they eat junk food (and that watching commercials also makes them more likely to eat other junk food later).

It’s well established that people eat unhealthy snacks when they veg out in front of the TV, and that might well be the reason why TV watching in particular is associated with weight gain and metabolic problems. In this study, TV time was positively associated with diabetes in women. The researchers noted that women who watched more TV ate more junk food and more calories, and fewer fish, vegetables, and fruits. They suggested that “the increased risk of diabetes associated with TV watching was largely mediated through obesity.” In this case, it’s not about sitting down on the couch; it’s about the bowl of Cheetos next to you.

There hasn’t been a study specifically on this, but it’s also possible that the blue light from TV watching late at night disrupts normal circadian rhythms, which throws off TV watchers’ sleep. This could very easily cause all kinds of health problems including weight gain: sleep deprivation is hands-down one of the worst possible things you can do for your body. But again, the problems here aren’t being caused by the sitting; they’re being caused by looking at blue light. The sitting is just incidental. It would be just as bad if you looked at the blue light standing up or lying down.

Sitting down to watch TV and sitting down to knit a scarf are both sitting. But TV-sitting is much more dangerous. This clues us in that there’s something going on here other than the sitting. If you really are looking to improve your health, that’s the thing to address!

Sitting Constantly vs. Sitting Occasionally

Besides the sitting-related behaviors, there’s also another problem with all the headlines screaming about how dangerous sitting is. All the sitting-smoking comparisons imply that the ideal would be absolutely no sitting at all. After all, there’s no such thing as a “healthy level of smoking.” It’s better to smoke one cigarette than two, but it’s even better not to smoke at all.

That’s not necessarily the case, though. And even if a 0-sitting environment were ideal, is that even possible? Would you want to stand or kneel at every meal? What if you needed to drive somewhere?

Fortunately, you don’t have to actually answer those questions, because it’s not sitting that kills. It’s constant sitting. Unlike cigarettes, there is a place for sitting in moderation.

Prolonged sitting (sitting for hours on end without a break or even a change in posture) is dangerous. Many of the studies showing the dangers of sitting were about people sitting for very long periods. To take an extreme example, this study supposedly proving that sitting reduces bone density was done in people on bed rest, which not even the most sedentary of couch potatoes are imitating.

But what if you get people out of their chairs during the day?

• This study found that quick breaks during 5 hours of prolonged sitting seriously reduced the dangerous effects on blood pressure.
• This study found that breaking up sitting time changed the expression of genes in muscle tissue. The breaks caused beneficial changes in the expression of genes that govern anti-inflammatory and antioxidant functions, blood lipids, and carbohydrate metabolism.
• This study found that adding walk breaks to a long period of sitting reduced cardiovascular risk by improving blood coagulation parameters.

In other words, there’s a difference between “sitting” and “sitting all day without a break.” The former is not totally ideal; the latter is downright dangerous.

Summing it Up

Demonizing “sitting” is pointless. For one thing, it’s fearmongering: the evidence doesn’t actually support the conclusion that every minute spent sitting is driving you closer to an early grave. For another, it’s not practically helpful. If someone has to sit for school or work (truck drivers, receptionists, most students), how does it help them to read all about how sitting is deadly? It doesn’t. But it does help to know…

• What types of sitting-related behaviors to avoid (blue screens late at night, snacking in front of the TV)
• That getting up for stretch breaks can be a health-saver.

And that brings us to Part 2: coming up next week, a practical guide to what you can actually do to reduce sitting and break it up in healthy ways.