COMMENTARY

Has Sitting Gotten a Bum Rap?

Aus Alzaid, MD

Disclosures

November 15, 2019

Aus Alzaid, MD

Looking for a moment of relief from the high-drama scene of the diabetes drug trials being presented at the 2019 European Association for the Study of Diabetes (EASD) meeting, I set out in search of something new and controversial. Before the end of the day, I stumbled on a treasure in a dimmed and quiet hall, marked by a poster announcing a debate about sedentary behavior. The motion for debate was: "The emphasis on sedentary behavior as lifestyle intervention target is entirely warranted."

Given what I had heard over the years about the menaces of sedentary behavior, I was expecting the outcome of the debate to be a forgone conclusion in favor of whoever spoke for the proposed motion. I even wondered why anyone would want to defend inactive physical behavior at a professional health-related conference.

But I soon learned how wrong I was in my initial reaction.

Thou Shalt Not Sit!

Speaking in support of the motion was David Dunstan, PhD, head of the physical activity laboratory at the Baker Heart and Diabetes Institute in Melbourne, Australia—a renowned expert in the field. He began his presentation with a simple but practical message: Being physically active is always relevant but not enough; we need to spend less time sitting as well.

His opening statement suggested a relationship between sedentary behavior and a list of metabolic and cardiovascular diseases. The best evidence was a study showing that the mortality curve dramatically accelerates once the sitting time exceeds a threshold value of 9 hours per day. Additional supportive evidence came from a large cross-sectional study demonstrating a 22% increased risk of developing type 2 diabetes (T2D) with each additional hour spent in a sedentary state. Dunstan noted that leading professional organizations are already catching up with the recommendation to sit less, as he displayed supportive statements published by the American Diabetes Association and other groups.

He then turned his attention to the benefits gained when a prolonged period of sitting is interrupted by short bouts of light physical activity. Even a simple change in posture (standing upright) can bring functional benefits, Dunstan suggested. He showed the results of elegant clinical studies conducted by his team in people with T2D: a short burst (3 minutes) of light physical activity (moving, stretching, or light walking) per hour of sitting resulted in substantial improvements (>30%) in daily glucose and insulin profiles of participating individuals.

He reminded everyone of the daunting realities currently facing people with T2D. One third of patients with T2D don't undertake any form of physical activity. Targeting sitting should be part and parcel of any future public health strategy. Slogans confined to "be more physically active" are not working. We need to change tactics and "take two shots at the target: sit less and move more," Dunstan concluded.

Let Sleeping Dogs Lie

Stepping forward to exonerate sedentary behavior from ill doings was Jason Gill, PhD, from the Institute of Cardiovascular and Medical Sciences in Glasgow, Scotland. He quickly made two interesting observations. First, he said, "You get the first 8 hours of sitting for free"; that is, there is no detrimental effect on health. We also know that the average sitting time reported by most people is 6-8 hours per day. Thus, Gill deduced that urging the public to sit less is unnecessary because such a call would be irrelevant to most people.

Second, existing evidence incriminating sedentary behavior has come largely from studies of TV viewing. Prolonged TV viewing is a recognized risk factor for obesity and metabolic diseases related to associated confounding factors (eg, snacking while watching TV). Sitting in itself is otherwise benign, Gill argued.

He then pointed out the difficulty of implementing strategies that target sitting. Moreover, any harms associated with prolonged sitting can be easily reversed by being sufficiently active at other parts of the day.

The impact of sitting 1 hour less is apparently equivalent in health benefits to that of walking for 2.5 minutes. Gill asked the audience which of these two acts they would rather undertake. Likewise, the relative risk of developing T2D with each additional hour of sitting can be readily eliminated by an additional minute of leisure-time physical activity. Public health interventions targeting sedentary behavior have yielded only modest reductions (37 minutes) in total sitting time per day. The change was even less pronounced if the public message was coupled with a "sit less" component, he said.

In contrast, the benefits of being more physically active are substantial and are easily attainable. He shared findings from recent trials conducted with his colleagues in Europe that demonstrated how an extra 6 minutes per day of measured, light physical activity (eg, stepping) substantially improved the physical, hemodynamic, and metabolic well-being of study participants. The study also showed a significant correlation between stepping action and cardiometabolic risk score.

Ultimately, a simple and focused message of "move more and more often" is sufficient and convenient, said Gill, adding that a "sit less" option is unwarranted, unnecessary, and would only confuse the public. And anyway, "Changing sedentary behavior is hard."

And the Winner Is…

After listening to both arguments and observing the reaction of the audience, I quickly realized that I had to make major adjustments in my general perception of the sedentary lifestyle.

It was clear from the outset that the only point of contention between the two speakers was whether to consider sitting as a viable public health target for intervention. The speakers otherwise shared identical views on the merits of exercise and the need for everyone to move more and more often.

Dunstan made a strong and instinctive argument against prolonged sitting. The scientific evidence he presented, however, was largely circumstantial. Gill's rational approach proved effective, although his final message lacked a measure of intuitiveness and foresight. Overall, I could say that I was swayed by the message of Dunstan but convinced by the argument of Gill.

It must be noted, however, that there's a general lack of long-term data (> 12 months) in this new and evolving field. I hope this will be addressed in future studies.

The Take-Home

Sedentary behavior is no longer the metabolic demon I once thought it was. I'm even tempted to propose the term "placid lifestyle" as an alternative to "sedentary behavior" to dispel the negative connotations associated with the latter. I've also learned to draw a distinction between ordinary sitting and the high-risk sitting associated with TV viewing.

I'm now reassured that sitting in the company of my iPad and reading or writing manuscripts, such as the one at hand, are safe and convenient habits. The news that the benefits of light physical activities are cumulative in nature did not escape my attention. We don't have to schedule time every day for such activities; the random bouts of activity taking place throughout the day should suffice (I hope).

Aus Alzaid, MD, is a consultant diabetologist living in Saudi Arabia. He has published widely in a variety of medical journals, including Diabetes Care, Diabetologia, the Journal of Clinical Endocrinology and Metabolism, and the Lancet.

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