Consequences of a Sedentary Lifestyle

June 21, 2022

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Shot of a man using a remote control while lying on the couch at home. Most people probably assume that the problem with a sedentary lifestyle is that you aren’t moving. (Yes, I see the tautology there.) Every minute, every hour, spent sitting at your desk or lounging on the couch is time you aren’t walking, lifting heavy things, or sprinting. That’s part of the problem with being sedentary, to be sure, and I’ll touch on that in this post. There’s more to it than that, though.

Sedentary behavior is defined as waking activities that generate less than 1.5 METs—sitting and lying down, basically. Experts recognize that even controlling for how much exercise a person gets, sedentary behavior per se is bad for physical and mental health. In other words, even if you hit the gym and walk the dog regularly, being sedentary is harmful.

Sedentary behavior isn’t just the absence of movement; it is the presence of something more insidious.

I’m sure I don’t need to tell you that sedentary behavior is more prevalent now than at any point in human history. Our grandparents’ generation was three times more likely to have moderately active jobs,¹ in ye olden days before so many of us sat in front of computers to work (I say as I type away on my laptop). Even though our ancestors probably enjoyed considerably more leisure time than the average adult today, their non-work time didn’t resemble modern repose. When hanging out in the shade of a tree or sitting around the campfire swapping tall tales, they adopted rest postures like the once-ubiquitous deep squat. Their bodies weren’t cushioned and held in a static position by a comfy sofa or La-Z-Boy. Muscles throughout their bodies were activated, tissues statically stretched. They shifted their posture often for comfort and balance.

In short, our ancestors rested, they enjoyed plenty of downtime, but they weren’t sedentary in the way we modern humans are. Sedentary behavior is an individual health problem, a public health problem, and an economic problem. The cost of medical care and lost productivity due to overly sedentary modern lives reaches the tens of billions of dollars every year. Today I’m going to outline some of the specific ways being sedentary hurts us and what we can do about it.

Being Sedentary Increases Disease and Mortality Risk

The data from large, long-term epidemiological studies tell a clear and consistent story: folks who are more sedentary in their day-to-day lives are at greater risk for just about every chronic disease. They also die sooner. It’s as simple as that… mostly. Some analyses do suggest that among the most active folks, those who get at least an hour of moderate to vigorous physical activity a day, the risks of being sedentary are attenuated.² I’ll return to that provocative finding later. For everyone else, there is a clear relationship between sedentary behavior, chronic disease, and shorter lifespan.

For example, a 2012 meta-analysis of studies with almost 800,000 combined participants found that the more sedentary you are, the greater your risk for suffering a cardiovascular event, succumbing to a cardiovascular event, or dying, period.³ The researchers went on to say that “the reported associations were largely independent of physical activity, adding further weight to the concept of sedentary behaviour [sic] being a distinct behaviour in its own right.”

That same meta-analysis found a particularly strong relationship between being sedentary and developing type 2 diabetes, as did a 2015 meta-analysis of studies that likewise controlled for physical activity level.⁴

The Cancer Prevention Study II (CPS-II) Nutrition Cohort study followed over 127,000 adults for two decades and tracked all manner of health outcomes.⁵ To understand the effect of being sedentary, the researchers compared people who sat for less than three hours a day at the beginning of the study to those who admitted to sitting for six or more hours per day. Controlling for variables such as alcohol use, smoking, diet, and chronic health issues, the more sedentary group had higher rates of, in the researchers’ own words:

“…mortality from all causes, cardiovascular disease (including coronary heart disease and stroke-specific mortality), cancer, diabetes, kidney disease, suicide, chronic obstructive pulmonary disease, pneumonitis due to solids and liquids, liver, peptic ulcer and other digestive disease, Parkinson disease, Alzheimer disease, nervous disorders, and musculoskeletal disorders.”

That’s quite a list. And once again, those findings remained after controlling for how much moderate to vigorous physical activity participants were getting.

Being Sedentary Creates Energy Surplus

One of the proposed mechanisms by which sedentary behavior increases disease risk is that it can lead to an energy surplus—eating more calories than you expend—which in turn leads to hyperglycemia, hyperinsulinemia, and insulin resistance.

Of course, not everyone who is sedentary also overeats. Researchers have tested whether folks who don’t overeat are protected against some of the negative consequences of being sedentary. At least in the short term, the answer seems to be yes.⁶ Being sedentary still carries risks, but being sedentary plus overeating is particularly dangerous. Possibly, this is why watching television is particularly detrimental. Researchers have long known that TV time is even more strongly associated with chronic disease and mortality than other types of sedentary behavior. The running theory is that people are also more likely to mindlessly snack in front of the television than, say, driving or sitting and reading a book.

There’s another issue to consider here. When you’re in an energy surplus, you’re also missing out on the benefits of being in a caloric deficit. In a new paper, scientists from Howard University coined the term “cellular exercise” to describe the cellular adaptations that result from hormetic stressors like, you guessed it, caloric restriction.⁷ Sitting plus overeating equals not getting the cellular exercise you need to thrive.

It Means You’re Not Walking

I won’t belabor this point because I’ve extolled the benefits of walking so often on the blog. Suffice it to say you should be walking as much as possible, as often as possible, on different surfaces. Walking is our birthright, and an imperative, as bipedal primates.

If walking isn’t already part of your daily repertoire, that’s priority number one. Start with this beginner’s walking routine.

Sitting Changes Your Biomechanics

My friend Katy Bowman has been hammering this home for years. Sitting and lying down put prolonged and undesirable loads on certain parts of the body, while others are underused. This leads to all manner of dysfunction. I’ll let Katy take it from here:

I’d break the problem of sitting into two categories. On one hand, there is the stillness. You are not moving so all of the systems in your body that depend on movement and the gravitational load to get things flowing aren’t happening.

But then there is the second piece that I like to call the geometrical problem. So it is not just that you are still; it is that when you are still, you are always assuming exactly the same position. You adapt to what you do most frequently and so you have all these changes in your physical structure like the length of your muscles, some getting longer, some getting shorter. You have lower input of what your weight is as far as your bones are concerned, so your bone density adjusts accordingly.

You (Might) Miss Out on the Benefits of Exercise

As I mentioned, exercise and sedentary behavior are separate constructs. You can be high on both, low on both, or any combination in between. That’s why many studies attempt to control for physical activity and take it out of the equation.

As I also mentioned, high levels of exercise seem to negate, or perhaps balance out, some of the harm of being sedentary. Researchers conducted a meta-analysis of longitudinal studies (ranging from 2 to 18 years of follow-up) covering more than a million adult subjects looking at the impact of sedentary behavior on all-cause mortality.⁸ Here’s what they found:

For individuals who got physical activity in excess of 35.5 MET hours per week (about 60 to 75 minutes of moderate intensity physical activity per day or more), it didn’t seem to matter how much they sat during the day. Sitting for 8 hours per day was no different than sitting for less than 4 hours. Everyone’s mortality risk was relatively low in this group.
The less exercise people got, the more being sedentary hurt in an almost linear fashion. By far, the worst combination was low exercise (only a few minutes of moderate exercise per day) and excessive sitting (more than 8 hours per day). Not surprising.
When they looked at TV time specifically, watching more than 5 hours per day was associated with higher mortality no matter how much a person exercised. As expected, though, the combination of inactivity plus more television watching was especially pernicious.

I’m not going to lie, I was surprised to dig into these findings. This high exercise-high sedentary group is the epitome of the “active couch potato” I’ve long warned against. These are your hardcore gym goers and endurance athletes who train hard then rest hard—maybe too hard, I believed. These newer data would suggest that at least where all-cause mortality is concerned, that pattern might not be as bad as once thought.

I’m willing to be wrong, but I’m not entirely swayed yet. At the end of the day, I always look at everything through a Primal, evolutionary lens, and that pattern still seems to represent an evolutionary mismatch. It may be that the effects take longer to show up or that they show up in ways other than mortality.

I also wonder about the possibility of healthy user bias here. If you’re doing 90 minutes of exercise and sitting for 8 hours, that still leaves 14.5 hours of time for sleeping and “other.” What happens during that other time matters. I’d venture to say that people who are this dedicated to exercise are, on average, probably more dedicated to other healthy practices.

Still, these findings suggest that if you’re going to sit on your butt for a third of your life, you’d better make sure you’re getting plenty of exercise too.

The Solution

You know what I’m going to say here: sit less, move more.

To be clear, I’m still not advocating for a lifestyle where you hit the gym for 90 minutes and then lie on the couch for the rest of the day. That’s not the way we are designed to live, period. Lift heavy things, yes. Sprint sometimes. Walk a lot. When you do sit or lie down, get up and switch positions frequently. Sprinkle microworkouts throughout the day.

Make a concerted effort to move during your workday. Create an active workstation. Give yourself various sitting, leaning, and standing options. Sitting on different surfaces—tall stools, backless benches, exercise balls—imparts different biomechanical stress. Go all in and invest in an underdesk treadmill or cycler.

I’m not saying don’t rest. Most people probably need more time to disconnect and recover from the stresses of the modern world than they’re currently getting. I’m saying don’t sit or lie for hours at a time unmoving. Instead of flopping on the couch after a long day of sitting at your desk and in your car, make your rest nurturing and restorative, and you’ll be much better off for it.