You are at higher risk of breast cancer if...

Girls who are underweight at the age of seven are more likely to develop aggressive types of tumours which are very difficult to treat when they get older, says a new study.

Breast cancer

Attention mothers! Feed your little daughters well as a new study has claimed that skinny young girls are at a greater risk of developing breast cancer later in life.

Researchers at the Karolinska Institute in Stockholm found that girls underweight at the age of seven are more likely to develop aggressive types of tumours which are very difficult to treat when they get older than those who are larger in size.

The study, published in the Breast Cancer Research journal, also showed that larger girls were less likely to develop what are known as "oestrogen receptor negative" tumours, one of the most deadly forms of the disease.

"It appears counterintuitive that a large body size during childhood can reduce breast cancer risk, because a large birth weight and a high adult BMI have been shown to otherwise elevate breast cancer risk," lead author Jingmei Li said.

"There remain unanswered questions on mechanisms driving this protective effect," she said, adding "given the strength of the associations and the ease of retrieval of information on childhood shape from old photographs, childhood body size is potentially useful for building breast cancer risk or prognosis models".

Surprisingly, they found that women who were bigger when younger were less likely to develop the disease in the menopause. Previous research has found that obese females are much more prone to breast cancer.

However, the scientists do not know why skinny girls are more likely to develop breast cancer but said their findings could have important implications in determining a woman's risk.

Breast cancer is the most common form of cancer in women and up to one in nine will get the disease at some point in their lives.