It’s possible to do regular exercise and still be a couch potato. And that inactivity can increase your cancer risk, said Charles E. Matthews, Ph.D., at today’s AICR conference session on Sedentary Behavior and Physical Activity. Matthews and other researchers are finding that sitting (being sedentary) too much is a separate health risk that needs to be studied separately from the health-protective effects of exercising.
“You can exercise 30 minutes a day, but if you sit the rest of the time your overall activity level is not that high,” he says. And it’s the total time you spending sitting that may be associated with cancer, according to Dr. Matthews (right), Physical Activity Epidemiologist and Investigator in the National Cancer Institute’s Division of Cancer Epidemiology and Genetics in Bethesda, Maryland.
Many adults spend 70 percent or more of their waking hours sitting — at desk jobs, in front of television and computer screens and in the car. On top of this inactivity, eating too much high-calorie convenience food has led to the obesity epidemic in this country, he says.
Too much sitting may be associated with an increased risk of cancer in several ways, according to Dr. Matthews and Neville Owen, PhD, a prominent inactivity researcher at Baker IDI Hart and Diabetes Institute in Australia. When a person sits too much, the mitochondria in our muscle cells don’t do their jobs, and as a result our energy metabolism it lower, increasing risk for weight gain.
Obesity has been linked with a wide range of cancers including colon, breast, endometrial and esophageal cancers among others, they said. Too much sitting also is linked to higher insulin levels which can influence cancer risk. Insulin is generally believed to increase the bioavailability of sex hormones and other growth factors that can promote some types of tumor growth.
A growing amount of data shows a connection between individual cancers, outlined by session chair Christine Friedenreich, PhD of the Alberta Health Services Cancer Care in Calgary, Canada. Physical activity clearly reduces risk of breast, colon and endometrial cancer risk and recurrence and possibly lung and prostate cancers, although more research is needed. From the precursors of cancer in cells’ DNA damage through diagnosis, physical activity plays and important role in improving quality of life and lower risk for other diseases. Cardiovascular disease is the main killer of breast cancer survivors later in life, because cancer patients are especially vulnerable to it due to the harmful effects of chemotherapy and radiation therapy including muscle loss, added Lee Jones, PhD, of Duke University. It’s vital for cancer patients to get more physical activity even as soon as they start therapy in order to maintain muscle and vascular health, he said.
But it’s never too late to start being more physically active to reduce risk. Dr. Matthews and Dr. Owens are reducingtheir own sedentary habits by overhauling their workspaces to stand up more easily while working. “I took out my modular furniture, and replaced it with a counter-height desk so I can either sit or stand and do my work,” Dr. Matthews said. He has put shelving on his treadmill handles to make space for his computer keyboard and mouse, and attached his monitor to the control panel on the treadmill.
“I can stand, walk, and type while looking straight ahead at the monitor,” he said. “I usually walk at a very slow speed so it’s easy to type. This isn’t intended to replace regular exercise – I still ride my bike to work on most days. But rearranging my office has given me the opportunity stand up and keep moving rather than just sitting for hours.” He has also placed his family’s computer workstation at home at standing height.
Small movements throughout the day as well as a half-hour set aside for physical activity can make a huge difference the researchers said. Dr. Matthews suggested that finding ways to reduce sitting by taking a movement break every hour or half-hour when possible, is a good way to increase overall activity levels.
“For instance, you can take the time to stand and prepare a meal from scratch rather than buying fully prepared or convenience foods. Other easy ways to increase activity is to do other things while watching TV, like standing and sorting laundry. Get up during commercials and take a walk around the house.”
This research was the subject of a major AICR press conference yesterday, and has made headlines around the world.