Overweight girls 'may have lower breast cancer risk'
Women who recall carrying excess body fat during childhood and adolescence appear to be less likely to develop breast cancer in later life, a US study reports.
However, Cancer Research UK pointed out that the findings do not mean being overweight is healthy.
Scientists at Brigham and Women's Hospital in Boston studied 188,860 women, all of whom were required to recall their levels of body fatness at five, ten and 20 years of age.
Of the participants, 7,582 developed breast cancer during the 17-year study period and the researchers discovered that the disease was less common in women who had been overweight as young girls or teenagers.
The link was found for both pre-menopausal and postmenopausal breast cancers and remained even when individuals' current weight had been taken into account.
Researchers noticed that the association between adolescent body weight and breast cancer risk was particularly strong in women who weighed less than 8.5 pounds at birth, and in those whose tumours did not have oestrogen receptors.
Publishing their findings in the American Journal of Epidemiology, the study authors concluded: "In this large prospective study, greater body fatness at young ages, particularly during adolescence, was associated with a substantial decrease in breast cancer risk. The inverse association was fairly linear, with no apparent threshold.
"Elucidating the mechanisms that explain the inverse relation of body fatness at early stages of life with risk of breast cancer may contribute to understanding of the causes of this important disease."
Nell Barrie, Cancer Research UK's science information officer, said: "These results might eventually tell us more about how breast cancer develops, but they don't mean that being overweight is good for you. Children who are very heavy are more likely to be overweight later on in life, and being overweight after the menopause increases the risk of breast cancer.
"Being overweight can also lead to at least six other types of cancer, including womb and bowel cancers, as well as diabetes, heart disease and other health problems."