An Hour of Moderate Exercise A Day May Offset Sedentary Behavior

Engaging in 60 to 75 minutes of moderate exercise per day may offset the risk of mortality in adults who sit for long periods of time, according to a new study.

Sedentary behavior has been linked to various health conditions and mortality over the years. Yet it is unclear whether increasing daily exercise level would affect the mortality risk associated with sedentary behavior.
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For their study, the researchers searched online databases for prospective cohort studies that provided data on daily sitting or TV-viewing time and physical activity, and reported estimates for all-cause mortality, cardiovascular disease mortality, or breast, colon, and colorectal cancer mortality. 

They included 16 studies that enrolled more than 1 million participants in their analysis.

The results showed that participants who sat for 8 hours per day and reported more than 35.5 metabolic equivalent of task (MET)-hours per week of exercise had the same mortality risk as those in the highest quartile of physical activity (>35.5 MET-hours per week and sat <4 hours per day).

Those in the second lowest quartile (<16 MET-hours per week and sat for <4 hours per day) and lowest quartile (<2.5 MET-hours per week and sat for >8 hours per day) of physical activity had a 12% to 59% increased risk of mortality than those in the highest quartile.

In addition, watching TV for 3 or more hours per day was associated with increased mortality regardless of exercise level; however, in the most active quartile, participants were only affected after watching TV for 5 or more hours per day.

“High levels of moderate intensity physical activity (ie, about 60-75 min per day) seem to eliminate the increased risk of death associated with high sitting time,” the researchers concluded.

“However, this high activity level attenuates, but does not eliminate the increased risk associated with high TV-viewing time. These results provide further evidence on the benefits of physical activity, particularly in societies where increasing numbers of people have to sit for long hours for work and may also inform future public health recommendations.”

—Amanda Balbi

Reference:

Ekelund U, Steene-Johannessen J, Brown WJ, et al; Lancet Physical Activity Series 2 Executive Committee, Lancet Sedentary Behaviour Working Group. Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women [published online July 27, 2016]. Lancet. http://dx.doi.org/10.1016/S0140-6736(16)30370-1.