Is it exercise or dieting that helps prevent cancer?

Scientists and health professionals have long believed that maintaining a healthy - or "ideal" - weight makes a difference in decreasing an individual's risk for cancer. But one lingering question is whether or not it's better, in terms of cancer prevention, if that weight is reached and maintained by dieting or by exercising.

In fact, researchers know that adults who gain just 10 pounds after the age of 30 significantly increase their risk of developing cancer. Many people either limit their diet to maintain their ideal weight or focus on being active and getting exercise. Given the current epidemic of obesity and a global population with high numbers of people who are overweight, the cancer rates will likely also continue to rise, along with numbers on the bathroom scale.

And Henry Thompson, director of Colorado State University's Cancer Prevention Laboratory, has some incisive questions: which one of these approaches makes the most difference for cancer prevention on a cellular level? Is it the weight, is it the exercise or is it the diet that makes the difference? And why are 10 pounds significant?

"Obesity and being overweight are destinations," said Thompson. "It's what got you there that is the problem, not just the fact that your weight is higher than it should be. The damage caused by the behavior that led to the weight problem started much earlier - before a person reached a point where he or she was overweight or obese."

Thompson's research is primarily focused on what physical activity and dieting contribute to breast cancer prevention. With a machine developed by engineering student Nick Fernandez at Colorado State, Thompson and his colleagues will use a laboratory model to evaluate the impacts of exercise on breast cancer prevention. The machine, which rewards exercise with food, permits Thompson to measure and study possible impacts of exercise intensity, speed, duration and frequency. The machine, which includes a computer-controlled exercise wheel, is a new concept in preclinical cancer research that Thompson developed specifically for this study.

The machine will allow Thompson to monitor the impacts of specific exercise and dieting combinations on breast cancer prevention to address questions such as: Is running better than walking? Are long exercise sessions more effective than short sessions? Is frequent exercise more important than sporadic exercise?

The research, based in Thompson's laboratory within the Department of Horticulture and Landscape Architecture, is funded by a $1.3 million grant from the National Institute of Health and a $165,000 grant from the American Institute of Cancer Research.

Specifically, the research will look for a relationship between exercise and risk for breast cancer. Thompson said that research will look for further clues in current evidence that indicates that some protection against cancer is due to the effects of physical activity that are distinct from, as well as related to, exercise's effects on adult weight gain.

"Little is known about how physical activity affects the risk for cancer," Thompson said. "We do know that people sit more at work than they used to, and that means that most individuals will need to intentionally exercise to increase physical activity."

Thompson's study will span four years and will look at the molecular and cellular differences exercise intensity, duration and frequency has on altering chemical activity, cellular proliferation and molecular pathways within the body that may trigger or help to prevent breast cancer.