Exercise before or after a sedentary work day may not reverse the damage sitting has done already, a new literature review study says.
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Daniela Schmid and Michael F. Leitzmann of the University of Regensburg in Germany looked at 43 observational studies, including 68,936 cancer cases, about the correlation between sedentary lifestyles and cancers. The authors found that the recommended amount of exercise — 150 minutes a week of moderate intensity aerobic activity and muscle-strengthening activities according to the Centers for Disease Control — will not undo the adverse effects of sitting.
The pair found that adults spend 50 to 60 percent of their day engaging in sedentary behaviors, including TV viewing, occupational sitting time and transportation. Results also indicated that average sitting time was associated with a 24 percent increase in colon cancer risk; a 32 percent increase of endometrial cancer risk; and a 21 percent increased risk of lung cancer.
“Adjustment for physical activity did not affect the positive association between sedentary behavior and cancer. This indicates that the increased risk of cancer seen in individuals with prolonged time spent sedentary is not explained by the mere absence of physical activity in those persons,” Schmid and Leitzmann wrote.
“Support is provided by observations of significant positive relations of TV viewing time to metabolic risk and mortality, even in physically active adults. That sedentariness has a detrimental impact on cancer even among physically active persons implies that limiting the time spent sedentary may play an important role in preventing cancer, even against the background of achieving the physical activity recommendations.”
Additionally, each two-hour per day increase in sedentary time was related to an 8 percent increased risk in colon cancer, a 10 percent increase in endometrial cancer risk and a “positive relation” between sedentary behavior and lung cancer.
The authors noted that TV viewing was often accompanied by other unhealthy behaviors such as eating unhealthy foods and smoking. As such, for every two hours a person increased their TV viewing time per day, researchers noted a 23 percent increased risk of obesity. By contrast, a two-hour per day increase of sitting at work increased one’s obesity risk by 5 percent.
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