New UBC Okanagan research shows that exercise can do more for breast cancer survivors than build strength-it may also increase levels of an appetite-suppressing hormone and control weight gain.
New UBC Okanagan research shows that exercise can do more than improve the strength and cardiovascular endurance of women who have survived breast cancer.
Dr. Sarah Purcell, a researcher with UBC's Southern Medical Program and Centre for Chronic Disease Prevention and Management , recently published a study examining how exercise affects breast cancer survivors undergoing estrogen-blocking therapy-a standard long-term treatment.
"Breast cancer survivors generally have favourable overall survival rates," says Dr. Purcell. "However, many have an elevated risk of weight gain, which can lead to obesity and eventual further complications such as heart disease and diabetes."
Obesity, she notes, can also lead to the recurrence of cancer, making it a serious concern for survivors and the medical community, which continues to puzzle over the exact cause of this weight gain.
"It's important to identify and understand the unique factors that cause obesity for this particular population," she says. "The underlying mechanisms for weight gain during endocrine therapy have not been fully explained but may relate to lower exposure to estrogen."
Dr. Purcell's latest study, published in Nutrition and Cancer , explored whether weight gain is linked to long-term estrogen therapy. More than 75 per cent of breast cancer survivors receive this treatment for five to 10 years, and when combined with chemotherapy can leave many with lower hormone levels.
To stay healthy during and after treatment, cancer guidelines recommend aerobic activities and resistance or strength training. These activities are particularly important for breast cancer survivors with obesity because they improve body composition and overall heart and metabolic health.
For the study, Dr. Purcell's team compared two randomized trials involving female breast cancer survivors and adults with obesity or high body weights. All participants were premenopausal before their cancer diagnosis and were currently receiving endocrine therapy.
"Our study shows that exercise can do more than build strength for these survivors-it may also help control appetite," she says. "Participants on estrogen-blocking therapy had higher levels of the appetite-suppressing hormone Peptide YY (PYY) after exercise than women without a history of cancer."
She says the results were surprising and opposite to what the team expected. Estrogen-blocking therapies are often linked to weight gain, but PYY is a hormone that helps reduce appetite.
"The breast cancer survivors had higher PYY levels right after exercise, which suggests their appetite-suppressing response lasted longer," says Dr. Purcell. "This unexpected result shows a novel interaction between exercise and estrogen suppression that has not been seen in healthy groups before."
Dr. Purcell says this may help explain how physical activity supports appetite control and weight management in women receiving breast cancer treatment. It also suggests exercise may help survivors manage weight by improving appetite control through hormones.
"Although the survivors didn't report feeling less hungry, their hormone levels showed a stronger appetite-reducing effect, and they ate less relative to their body size following exercise," she adds. "Exercise may help manage treatment-related weight changes by tapping into natural appetite-control systems, something we weren't expecting to find."
