Too Much Sitting Tied to Risks for Certain Cancers
Those with the most chair time had worse odds for colon, endometrial cancers, researchers suggest
Moreover, every two-hour increase in sitting time was linked to an 8 percent increased risk of colon cancer and a 10 percent increased risk of endometrial cancer.
The risks remained even for "active couch potatoes" -- folks who squeeze in some time at the gym but still spend most of their day off their feet. This suggests that regular exercise can't offset the risks of too much sitting, the study authors said.
The findings, published June 16 in the Journal of the National Cancer Institute, make sense to Dr. Graham Colditz. He's the associate director for prevention and control at Washington University's Siteman Cancer Center in St. Louis.
"High blood sugar and high insulin is a clear sort of pathway to colon cancer, and we know from intervention studies that walking lowers insulin and getting up after meals lowers blood sugar compared to sitting," said Colditz, who was not involved in the research.
As for endometrial cancer, "Obesity is a phenomenally strong cause. In fact, it is the main modifiable risk factor for endometrial cancer," he said.
"So for me, the likely scenario there is that the sitting, the weight gain and obesity really go together and exacerbate the risk of endometrial cancer," he added.
Because the studies included in the review only looked at broad relationships, they can't prove that sitting, by itself, causes cancer. But the findings appeared to be remarkably consistent across studies, so Colditz thinks they should be taken seriously.
The study authors agree.
"Cutting down on TV viewing and sedentary time is just as important as becoming more active," said Schmid. "For those whose jobs require them to sit at a desk most of the day, we recommend breaking up the time spent sitting by incorporating short bouts of light activity into the daily routine," she added.