The study is the first to suggest that a "negative energy balance" - produced by increasing the mice's energy output by use of a running wheel, while maintaining a restricted calorie intake - appeared to be the important factor in inhibiting the growth of polyps, which are the forerunners of colorectal tumors, says lead author Lisa H. Colbert, assistant professor in the UW-Madison department of kinesiology.
For the study, Colbert and her co-authors used mice with a genetic mutation that predisposed them to develop intestinal polyps.
"Our studies are relevant for humans in that these mice have a mutation in one of the same genes, APC, that is also mutated in human colon cancer," she explains. "The protective effect of exercise and lower body weight in our mice is consistent with epidemiological evidence in humans that suggests higher levels of activity and lower body weight reduces the risk of colon cancer."
Mutations in the APC gene in humans are responsible for an inherited condition called familial adenomatous polyposis (FAP). This condition affects about one in 10,000-15,000 people worldwide, and 95 percent of those affected develop polyps in the colon that eventually progress into cancer, usually before age 40.
The researchers randomly assigned seven-week-old male mice to either voluntary wheel running or to no exercise for 10 weeks.
Over the course of the study, the no-exercise control group consumed as much food and water as they wanted. For the first three weeks, the exercising mice received as much as those in the control group. After that, the active mice were restricted to the amount of food and water that the control group received th
Contact: Lisa H. Colbert
University of Wisconsin-Madison