People who spend too much time sitting down could increase their risk of developing cancer, even among those who exercise regularly, according to new research from the American Institute for Cancer Research.
Research data shows that about 100,0000 new cases of breast and colon cancer each year can be connected to a lack of physical activity.
Dr. Neville Owen, who studies the effects of sedentary behavior at the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, has estimated most people actually sit for 15.5 hours each day.
He told ABC News the connection between sitting and cancer lies in physiological changes that occur when the body is inactive for long periods of time.
"When you're sitting, the big muscles, especially in lower part of body, are completely unloaded. They're not doing their job," Owen said.
That inactivity prompts changes in the body's metabolism, Owen said, and produces a number of biological signals, what scientists call biomarkers, which are linked to cancer.
"It's been surprisingly consistent with what strong relationships there are between physical inactivity and these biomarkers of cancer risk," Owen said.
The research center recommends 30 minutes of physical activity a day, but they say the other hours also matter.
They say just getting up and walking around every 60 minutes can cut the risk of cancer.
The U.S. Centers for Disease Control and Prevention says that adults should get 150 minutes of moderate-intensity exercise, or 75 minutes of vigorous exercise, each week, along with weekly muscle-strengthening activities.