Voluntary exercise and a restricted diet reduced the number and size of pre-cancerous polyps in the intestines of male mice and improved survival, according to a study by a University of Wisconsin-Madison research.
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.”
The researchers randomly assigned seven-week-old male mice to either voluntary wheel running or to no exercise for 10 weeks.
“The exercising mice ran an average of 3.8 km a day, and the further they ran the fewer polyps they had. Exercise significantly reduced total polyp number and polyp size, as well as prolonging survival,” says Colbert.
In this study, female mice that had 24-hour access to running wheels and were exposed to ultraviolet B light (UVB) took longer to develop skin tumors, developed fewer and smaller tumors, and had decreased amounts of body fat compared to mice that did not have access to running wheels. The researchers emphasized that it was unknown yet whether exercise decreased the risk of sunlight-induced skin cancer in humans, and clinical trials were needed to investigate this further.