Does a New Study Really Debunk Dangers of Prolonged Sitting?

Sitting Too Much

Story at-a-glance -

  • New research found participants’ risk of premature death was not influenced by their sitting time
  • The lack of association between sitting and mortality may have been due to a “higher than average daily activity” level among the study participants
  • Sitting less and moving more is associated with a number of positive health outcomes for obesity, diabetes, heart disease, and more

By Dr. Mercola

Accumulating evidence suggests that the high levels of physical inactivity (i.e. sedentary time) in America are greatly increasing Americans' risk of chronic disease and premature death.

Compared to those who exercise often and are hardly sedentary, those who rarely exercise and spend a lot of time sedentary have an almost eight-fold increased risk of dying prematurely.1

Sedentary time includes not only the time you spend sitting on your couch and in your vehicle, but also, for many, time spent sitting at a desk at work. On average, a US adult spends nine to 10 hours each day sitting,2 which is so much inactivity that even a 30- or 60-minute workout can't counteract its effects.3

The case, it seemed, was closed that in order to be optimally healthy, reducing this sitting time drastically would be essential for most Americans. And then, in October 2015, research published in the International Journal of Epidemiology came out stating sitting time was not associated with mortality risk, according to their data.4

The media began printing headlines like "Couch Potatoes Rejoice! Sitting for Long Periods Is NOT Bad for Your Health, Study Claims." So is it true that you can sit for the majority of your waking hours and not suffer any health consequences? Let's take a closer look at the study in question…

Sitting for Long Periods Doesn't Increase Risk of Death: Really?

Researchers from the University of Exeter and University College London evaluated data from more than 5,000 people, including their total weekly sitting times, walking levels, and physical activity.

The participants' risk of death was not influenced by their sitting time, even after adjusting for diet and other health factors.

There are several factors why this finding may not be as cut-and-dried as the media would have you believe. For starters, the researchers noted the lack of association between sitting and mortality may have been due to a "higher than average daily activity" level among the study participants.

In other words, the group of people studied may be less sedentary than the average American. Further, the study is a "cohort" study, which relies on the participants' recollection along with physician reports. Studies such as this are considered observational and may not be as reliable as controlled studies.

The study also assessed only overall mortality, not specific health outcomes like diabetes or obesity, which might have yielded different results. The data was collected from 1985 to 1999 as well, when eating habits were likely to be quite different than they are today more than a decade later.

The study also used "person years" rather than actual years, which is a measure of the number of years that the group of participants has spent in the study. In other words, there were no real controls used, so the measurement had to be adjusted using person years instead of actual years.

A prior study based on the same cohort sample and conducted by the same lead researcher similarly concluded that sitting time was not associated with obesity.

Rather, the conclusion was that obesity was associated with more time spent watching TV (but not other types of sitting).5

This study also acknowledged that part of it is based on the recollections of the participants, which can be notoriously inaccurate.

A Lack of Movement May Be Most Detrimental of All

Collectively, the above-mentioned factors may explain why the featured cohort study did not find an association between sitting time and risk of premature mortality. However, a statement by study author Melvyn Hillsdon of the University of Exeter may provide the most revealing reason of all:6

"Our study overturns current thinking on the health risks of sitting and indicates that the problem lies in the absence of movement rather than the time spent sitting itself… Any stationary posture where energy expenditure is low may be detrimental to health, be it sitting or standing."

This may be key, and as you cut back on sitting, the point is not to simply stand still instead. According to Dr. James Levine, author of the book Get Up!: Why Your Chair Is Killing You and What You Can Do About It:7

"I think it's correct to say we're in the middle of a 'stand up movement,' but the emphasis needs to be on movement… I don't want people to think that they should stand up like still soldiers. That is not a good idea."

Yet, when you make a conscious effort to stand up instead of sit, such as by using a standing work-station, you'll probably move more naturally as well. According to Dr. Levine:

"When somebody gets a standing desk, they generally stand for several hours a day. But they don't stand still. A couple of things happen. The first thing that happens is, they generally move from leg to leg and generally change their body posture quite a lot.

That weight-bearing and adjustment of weight-bearing has a whole series of physiological benefits to the musculature, the balance in musculature, the visual cortex, the testicular system, and so on."

Research by Dr. Levine and colleagues showed, for instance, that the installation of sit-stand desks reduced sitting time during a 40-hour workweek by eight hours and reduced sedentary time by 3.2 hours. Further, the participants enjoyed having the option of a sit-stand desk, which was also associated with increased sense of well-being and energy, and decreased fatigue while having no impact on productivity.8

Ideally, Replace Sedentary Time with Active Movement

The more you can replace a sedentary activity, like sitting, with an active one, the better. This is one reason why I recommend setting a goal of taking 10,000 steps a day – it helps keep you moving and gives you a concrete number to work toward. (This is in addition to your regular exercise program, not in place of it.)

If you work a desk job, you obviously must spend some time either sitting or standing, but this can often be interspersed with regular movement. For instance, you can pace while talking on the phone and break up periods of sitting or standing by doing simple exercises at your desk.

Even movements such as fidgeting appear beneficial. Among women who reported sitting for seven hours or more a day and hardly fidgeting, the risk of all-cause mortality increased by 30 percent. Women who reported fidgeting often fared far better – after sitting for five to six hours a day, their risk of mortality decreased. Further, there was no increased mortality risk from longer sitting time in either the "middle" or "high" fidgeting groups.9

Another example, people who made a point to get up and walk around for two minutes out of every hour increased their lifespan by 33 percent compared to those who did not.10 Those who stood up for two minutes an hour did not reap the benefits that those who walked for two minutes did.

Recent research even showed that it takes just three hours of sitting to cause damage to blood vessels, but when the sitting time was interrupted by a gentle 10-minute cycling session, no decline in vascular function was recorded.11

So while it's clear that excessive sitting isn't healthy, it's likely that excessive standing isn't either. The "happy middle" is changing your position regularly and often throughout the day and keeping active. Ideally, I recommend sitting for no more than three hours total each day. Alan Hedge, a Design and Ergonomics professor at Cornell University, suggested a slightly different approach in the Boston Globe:12

"Sit for no more than 20 minutes at a time, Hedge recommended, and stand in one position for no more than 8 minutes. You should also take a two-minute moving break at least twice an hour to stretch or walk around."

What Does the Research Say About Excessive Sitting?

It's important to understand that there is a vast body of research confirming the health consequences of spending too much time in a sedentary state such as sitting. Recent research published in Diabetes Care revealed, for instance, that more sedentary time was independently associated with insulin resistance, diabetes, and impaired glucose tolerance.

Each additional hour per day of sedentary time was associated with 3 percent higher fasting insulin resistance. Previous research published in Diabetologia found those who sat for the longest periods of time were twice as likely to have diabetes or heart disease compared to those who sat the least.13

Sitting for more than eight hours a day has also been associated with a 90 percent increased risk of type 2 diabetes.14 Research published in the Journal of the American College of Cardiology also showed that women who sit for 10 or more hours a day may have a significantly greater risk of developing heart disease than those who sit for five hours or less.15 And findings presented at the 2015 Inaugural Active Working Summit found sitting increases:16

  • Lung cancer by 54 percent
  • Uterine cancer by 66 percent
  • Colon cancer by 30 percent

Writing in the Cleveland Clinic Journal of Medicine, Neil Skolnik, MD further noted:17

"A recent scientific advisory stated that the elimination of health risk behaviors, including poor-quality diet, excess energy intake, physical inactivity, and smoking might prevent 80 percent of heart disease, stroke, and type 2 diabetes mellitus, as well as 40 percent of cancers. Recently studies have shown that sedentary time, as a separate indicator from exercise, confers an increased risk for mortality… Clearly, it is time to take a break from reading and get up and take a walk."

What's It Like to Break Free from Excessive Sitting?

Many people feel better nearly immediately when they swap sitting for standing and regular movement. As one worker who uses an adjustable-height work desk told TIME:18

"I definitely feel healthier standing while working as it causes me to be more focused on my posture and 'hold' myself better in terms of my stomach and shoulders especially."

Personally, standing more has worked wonders for me. I used to recommend intermittent movement, or standing up about once every 15 minutes, as a way to counteract the ill effects of sitting. Now I've found an even better strategy, which is simply not sitting.

I used to sit for 12 to 14 hours a day. Now, I strive to sit for less than one hour daily. After I made this change, the back pain that I have struggled with for decades (and tried many different methods to relieve without lasting success) has disappeared. In addition to not sitting, I strive to walk about 10,000 to 15,000 steps a day, in addition to my regular exercise program.

I believe this combination of exercise, non-exercise activities like walking 10,000 steps a day, along with avoiding sitting whenever possible is the key to being really fit, and enjoying a pain-free and joyful life. Many progressive workplaces are helping employees to stand and move more during the day.

For instance, some corporations encourage "walk-and-talk" meetings and e-mail-free work zones, and offer standing workstations to those who are interested. But if yours isn't among them, take matters into your own hands. You may be used to sitting down when you get to work, but try, for a day, standing up instead. Keep an open mind and see how you feel… As Dr. Levine said:

"We live amid a sea of killer chairs: adjustable, swivel, recliner, wing, club, chaise longue, sofa, arm, four-legged, three-legged, wood, leather, plastic, car, plane, train, dining, and bar. That's the bad news. The good news is that you do not have to use them."

For more information, you can watch my interview with Dr. Levine below.


Download Interview Transcript

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