A new analysis found that prolonged sitting and a lack of physical activity could be the cause of more than 90,000 new cases of breast cancer and colon cancer reported each year.

The new data, being presented Friday at the annual conference of the American Institute for Cancer Research (AICR), linked inactivity to 49,000 cases of breast cancer and 43,000 cases of colon cancer. According to Alpa Patel, an American Cancer Society epidemiologist who looked at the data, the numbers “seem like very reasonable estimates.”

Patel and others have investigated the dangers of sitting too long without moving around, which is now referred to as “sitting disease,” and agree that prolonged sitting can be harmful to health. In a study of 123,000 people, she discovered that participants had a higher risk of dying early the more time they spent sitting.

“Even among individuals who were regularly active, the risk of dying prematurely was higher among those who spent more time sitting,” she said. Patel says having a regular exercise routine isn’t enough. She said that even if you’re doing half an hour of aerobic activity a day, you need to make sure you aren’t just sitting the rest of the day.

“You have to get up and take breaks from sitting,” said Patel.

James Levine, a professor of medicine at Mayo Clinic, agrees. Most people sit an average of seven to nine-and-a-half hours a day and “if you’ve sat for an hour, you’ve probably sat too long,” he said.

Doctors and researchers have long believed that physical activity decreases the risk of many chronic diseases, including cancer, heart disease and diabetes. But, according to new research, there is evidence that, in the case of certain cancers, inactivity could actually increase the risk. Epidemiologist Christine Friedenreich reviewed more than 200 cancer studies from across the world and found that prolonged sitting increases the risk of some types of cancer, including colon, endometrial and ovarian cancers.

Friedenreich also found credible evidence that regular physical activity can reduce the risk of breast cancer, colon cancer and endometrial cancer by as much as 25 or 30 percent.

Alice Bender, a registered dietician with AICR, agreed, saying, “A brisk daily walk of at least 30 minutes could lower a person’s risk over time for breast cancer and colon cancer.”

Friedenreich said the new analysis is a conservative estimate, but that it “gives us some idea of the cancers we could prevent by getting people to be more active. The more physical activity you do, the lower your risk of these cancers.”

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