Exercise has many benefits, but you might not have thought it could help protect against skin cancer.

In mice, however, that is the case.

In a new study, two groups of mice were exposed to ultraviolet B (UVB) light, which is known to cause skin cancer. The group that had a running wheel developed 32 percent fewer tumors. The tumors developed more slowly and were smaller than in the group that did not have gym access.

The research is detailed in the May 13 issue of the journal Carcinogenesis.

What's going on

Follow-up research not published in the journal indicates a possible reason for the difference. Exercise enhances a process called UVB-induced apoptosis, which means programmed cell death. This is a good thing: It kills sun-damaged cells.

"While UVB is triggering the development of tumors, exercise is counteracting the effect by stimulating the death of the developing cancer cells," said study leader Allan Conney of Rutgers University.

Skin cancer, or melanoma, is the most common form of cancer in humans. It kills more than 7,000 people in the United States each year, according to the American Academy of Dermatology.

Link to weight

The new mouse study revealed another interesting result. The rodents that exercised at more and their body fat was reduced, so the scientists now see a possible link between lower body fat and fewer tumors.

"This relationship between body fat and tumors may also play an important role in carcinogenesis and warrants further investigation, particularly with obesity on the increase in the Western world," Conney said.

The scientists stress that their conclusions are based on laboratory studies on mice, and it is not known if exercise lowers the risk of skin cancer in humans.

However, research published last June in the journal Cancer Epidemiology, Biomarkers & Prevention suggested that exercise and weight control reduce the risk of breast cancer. Other studies have shown that exercise reduces a person's risk of developing bowel cancer and colon cancer. And research presented last year at a meeting of the American Society of Clinical Oncology found those treated for stage III colon cancer could reduce the risk of recurrence 40 to 50 percent through exercise.

Meanwhile, several studies have shown that exercise improves the overall health of people who have cancer.

Indoor Tanning Addictive, Study SuggestsNew Noninvasive Imager Detects Deadly Melanoma EarlyCancer Takes Over Top Spot as Killer of Americans Under 85Gold Probes Could Reveal Cancer in Your Body