Postmenopausal adiposity benefits with increasing aerobic exercise

By Shreeya Nanda, Senior medwireNews Reporter

An aerobic exercise regimen of 300 min/week versus 150 min/week significantly improves adiposity outcomes among postmenopausal women, shows research published in JAMA Oncology.

Additionally, the benefits of higher-volume exercise could include “possibly a lower risk of postmenopausal breast cancer”, say Christine Friedenreich (Alberta Health Services, Calgary, Canada) and co-authors. They explain that “[a] probable association between physical activity and postmenopausal breast cancer risk is supported by more than 100 epidemiologic studies, with strong biologic rationale supporting fat loss as an important (though not the only) mediator of this association.”

The Breast Cancer and Exercise Trial in Alberta (BETA) enrolled cancer-free postmenopausal women aged between 50 and 74 years who had a body mass index (BMI) of 22 to 40 kg/m² and did not regularly exercise. Participants were randomly assigned to complete either 300 min/week or 150 min/week of moderate to vigorous aerobic exercise.

After 12 months, the 189 women in the high-volume exercise group experienced significantly greater total body fat loss than the 195 in the moderate-volume group, at least-squares mean change in mass of –2.41 kg versus –1.45 kg, equating to –2.2% versus –1.2% of body fat.

As measured by computed tomography, subcutaneous and total abdominal fat area, but not intra-abdominal fat area, were also significantly reduced in the high- compared with moderate-volume group, at least-squares mean changes of –34.5 cm² versus –23.7 cm² and –47.8 cm² versus –35.6 cm², respectively.

And decreases in BMI, waist circumference and waist-to-hip ratio were also significantly greater in women who followed the high- versus the moderate-volume exercise regimen.

The researchers identified an association between exercise group and baseline BMI, such that women with baseline BMI of at least 30 kg/m² reaped more benefits from high-volume exercise with respect to weight and subcutaneous abdominal fat loss, and reductions in BMI, waist and hip circumference than their counterparts with a lower BMI.

Addressing the issue of adherence, they note that even though the participants were “mostly” younger than 70 years of age and motivated to exercise, “adherence was challenging”. Median adherence during the study period, excluding the initial 12-week ramp-up period, was 254 min/week for the high-volume group and 137 min/week for the moderate-volume one, reflecting 85% and 91% of the target amounts, respectively.

Commentator Kerri Winters-Stone (Oregon Health and Science University, Portland, USA) says in an accompanying piece that although the study confirms that “more exercise is better in terms of fat loss, the implications of this in terms of reducing disease risk may be undersold.”

“In the context of breast cancer, the degree of fat loss experienced by women exercising nearly 100 minutes more per week only equated to an estimated 2% further reduction in risk of breast cancer–probably not enough to motivate women to add more than an hour and a half more exercise to their weekly schedule.”

But she adds that “[t]he cancer-fighting power of exercise likely extends beyond its fat-fighting benefits to include changes in cellular and molecular pathways of cancer development—hypotheses worthy of exploration in future dose-response trials.”

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