A new study suggests that women who are overweight or have high blood sugar levels could be more at risk of developing aggressive breast cancer.
The report, which is published in the journal Breast Cancer Research and Treatment, is believed to be the first to look at how excess body fat and blood sugar levels affect the chance of developing different types of tumours.
A team from Umea University in Sweden carried out the study, and they found that while women had a decreased risk of low-risk breast cancer if they were overweight or suffered high blood sugar (insulin resistance), they were at higher risk of more aggressive tumours.
The study, which was funded by the World Cancer Research Fund, looked at blood samples and other measurements including body mass index (BMI) taken from more than 1,000 women.
Of the group, 561 women had been diagnosed with breast cancer while 561 remained free of the disease and acted as a control.
The women were aged 52 on average at the point of recruitment and the average time to diagnosis was 4.4 years.
The study found that the association of BMI, leptin (a hormone linked to body fat) and HbA1c (a blood sugar reading) and breast cancer risk differed significantly according to whether the tumour was diagnosed as early stage I or more advanced stages II to IV.
"Elevated levels of these factors were inversely associated with stage I breast cancer, but were generally related to an increased risk of stage II-IV disease," the authors said.