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People who sit too much every day are at an increased risk of diabetes, heart disease, cancer and shorter life spans, even if they exercise, a new study finds.

“More than one-half of an average person’s day is spent being sedentary — sitting, watching television or working at a computer,” David Alter, a senior scientist at the University Health Network in Toronto and the study’s senior author, said in a statement. “Our study finds that despite the health-enhancing benefits of physical activity, this alone may not be enough to reduce the risk for disease.”

Researchers looked at 47 studies examining the relationship between sitting and mortality, according to the findings, published last week in the journal Annals of Internal Medicine. They found that people who sat for long periods were 24 percent more likely to have died from health problems during the studies, which lasted between one and 16 years, than people who sat less.

The 47 studies didn’t use a standard cutoff to define how much sitting was too much, but “if you sit more than eight hours [a day], that’s probably linked to a lot of the negative health effects,” said the study’s lead researcher, Aviroop Biswas, a doctoral candidate at the University of Toronto.

The researchers also found that excessive sitting was associated with an 18 percent increased risk of dying of cardiovascular disease and a 17 percent increased risk of dying from cancer during the study periods. Sitting for too long was tied to a 91 percent increased risk of getting Type 2 diabetes, and to increases of about 13 and 14 percent in the risk of being diagnosed with cancer or heart problems, respectively.

What goes wrong in our bodies when we park ourselves for nearly eight hours per day? A chain of problems from head to toe.

Among studies that looked at cancer type, sitting for too long was associated with a higher risk of being diagnosed with, or dying of, breast, colon, colorectal, endometrial and ovarian cancers, the researchers found.

The researchers also found that the people who exercised generally faced lower risks of these health conditions than those who didn’t exercise. But exercising did not completely counteract the risks that came with sitting for a long time. For example, people who sit for long periods but also exercise were one-third less likely to die during the studies than the people who reported little or no exercise, according to 10 of the 47 studies.

Other research has linked increased sitting with health problems, but this analysis is one of the largest and most rigorous, and included nearly 830,000 people who died from health problems, 550,000 people who developed heart problems and 745,000 people who developed cancer, the researchers said.

People can increase their activity levels by trying to stand more, such as when they’re eating a snack or taking public transportation.

“Moments when you’re sitting, think of ways to stand,” Biswas said. “Move as much as you can when you’re not exercising.”

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