Having too much body fat increases a person’s risk for developing at least 12 types of cancer, including postmenopausal breast cancer. Scientists rely on several techniques to assess body fatness but whether one method provides a more accurate measure of risk than another is unclear. Findings from a new study, published earlier this year in the International Journal of Cancer, suggest that body fatness is linked with increased risk of postmenopausal breast cancer, regardless of how it is measured.
The study was based on data collected from a large subset of participants enrolled in the UK Biobank, a long-term prospective cohort study of more than 500,000 adults between the ages of 40 and 70 years living in the United Kingdom. The subset used in the current study comprised of more than 162,000 postmenopausal women whose health was followed for approximately eight years.
At the time of enrollment, the women provided information about their lifestyles, health, medical history, and socio-demographics. Trained staff assessed the women’s body composition using three distinct measurement methods: waist circumference, body mass index, or BMI, and bioelectrical impedance. Bioelectrical impedance is considered a more accurate assessment of body fatness than waist circumference or BMI.
Cancer diagnoses were obtained from national cancer incidence databases. More than 2,900 women were diagnosed with breast cancer during the study period.
Women were categorized into quartiles of body fatness based on each candidate measure: BMI, waist circumference, and body fatness. All measures of body fatness were linked with a dose-responsive increased risk of postmenopausal breast cancer; as body fatness increased, so did breast cancer risk. The women in the highest category of body fat mass (greater than 32kg) were 70 percent more likely to develop breast cancer compared to women in the lowest category body fatness.
The effect of body fatness was greater in older women than in younger women: Those who had been postmenopausal for the longest time (12 years or more) were nearly 40 percent more likely to develop breast cancer, compared to women who had been postmenopausal for less than 12 years.
Large waist circumference contributes to increased risk of many diseases such as diabetes and heart disease because visceral fat – the type of fat that is stored in the abdominal area, where the waist is measured – is more metabolically active and is associated with detrimental effects on insulin sensitivity and other factors. However, this study suggests that the role of waist circumference in increased cancer risk is related merely to its contribution to overall body fatness.
Researchers have not yet identified the exact mechanisms to account for the link between body fatness and cancer risk. However, in postmenopausal women, one explanation may lie with estrogen production in fatty tissue, the primary source of estrogen after menopause. High estrogen levels may promote cancer by increasing cellular proliferation and angiogenesis – the development of a blood supply – and preventing apoptosis, a type of programmed cell death that would normally eliminate damaged cells.
The findings from this study suggest that overall body fat is the “smoking gun” – a key predictor of postmenopausal breast cancer risk among women. Maintaining a healthy weight can help reduce the risk of many types of cancer and other chronic diseases.
Learn more about reducing your risk of breast cancer from AICR’s Cancer Sites.
This study was funded by Cancer Research UK.