WASHINGTON -- An American study suggests regular exercise could add to the life expectancy of breast cancer survivors because it lowers their heightened risk of cardiovascular disease, diabetes and possibly breast cancer recurrence.

"Many people don't know the number one cause of death for breast cancer survivors is heart disease, not cancer," said Christina Dieli-Conwright, lead author of a study published in the Journal of Clinical Oncology on Monday.

The study suggests female breast cancer survivors should engage in a mix of aerobic and resistance exercise to reduce their increased risk for metabolic syndrome -- a cluster of health conditions that includes high blood pressure and excessive body fat.

"In breast cancer patients, metabolic syndrome is exacerbated by obesity, a sedentary lifestyle and receipt of chemotherapy," said Dieli-Conwright, an assistant professor of research at the University of Southern California Division of Biokinesiology and Physical Therapy.

Women with metabolic syndrome are three times more likely to experience breast cancer recurrence and two times more likely to die from breast cancer, the study cited.

Obesity can cause inflammation, which may promote tumor growth and cause cancer recurrence, said Dieli-Conwright.

In a previous study, she analyzed blood samples and fat biopsies from 20 obese patients. She found that exercise improved systemic inflammation and reduced inflammation in fat cells.

"Exercise is a form of medicine," Dieli-Conwright said. "Both of these studies support that idea, and we will continue to conduct studies to supplement traditional cancer therapies."