High Total Body Fat Increases Risk of Postmenopausal Breast Cancer

A loss of overall body fat, rather than abdominal fat, is associated with lower levels of breast cancer markers, according to a new study.

Research has shown that increased levels of the blood markers testosterone and oestrogen, sex hormones, leptin, and inflammatory factors are associated with breast cancer risk.

However, studies examining these markers have had contradictory findings, with some suggesting that the markers are primarily produced in fat accumulated in the stomach, while others have shown that weight loss is associated with changes in blood levels of breast cancer markers.

In a study published in Endocrine-Related Cancer, investigators sought to assess the associations between changes in total fat and abdominal fat and changes in biomarkers for breast cancer risk.

The investigators used data from the SHAPE-2 trial of 243 postmenopausal overweight women. The intervention in the trial consisted of a loss of 5 kg to 6 kg (11 lbs to 13 lbs) either by diet only or exercise plus diet.

After 16 weeks, the investigators measured serum sex hormones, inflammatory markers, total body fat, and intra and subcutaneous abdominal fat. X-ray and MRI-based scans were used to assess changes in total and abdominal fat. The levels were then compared with those taken prior to the weight loss.

The results of the study showed that a reduction in total body fat was associated with favorable changes in free oestradiol, free testosterone, leptin, and sex hormone-binding globulin (SHBG). Loss of intra-abdominal fat was associated with a decrease in free testosterone, high-sensitivity C-reactive protein (hsCRP), and leptin, as well as an increase in SHBG.

The results of the multivariable analysis found that the best fitted model for the biomarkers free oestradiol, SHBG leptin, and adiponectin included only total body fat. Whereas free testosterone was subcutaneous abdominal fat. For Il-6 and adiponectin, only intra-abdominal fat change was important, according to the study.

“It is known that belly fat increases the risk of several chronic diseases, independently of total body fat, but for reducing sex hormone levels total body fat seems more important,” said lead investigator Dr Evelyn Monninkhof.

Prior research has shown conflicting associations between breast cancer risk and belly fat, but in the current study, investigators used a more accurate scanning-based method to determine fat distribution rather than waist circumference.

“In our population of healthy overweight postmenopausal women, we found fat loss at different body locations was associated with changes in different types of biomarkers, known to be related to breast cancer risk,” the authors wrote.

For the study, investigators obtained 2 measurements of fat depots and biomarkers over time. Additionally, they used more accurate DEXA measurements for total body fat, as well as MRI for belly fat.

“Our next step is to find out how belly fat and total body fat can best be conquered, to identify which nutritional or physical activity programs are optimal for reducing both weight gain and breast cancer risk,” Dr Monninkhof concluded.