Women who were obese or overweight before and after being diagnosed with breast cancer have lower odds of surviving the disease, a recent study suggests.

Researcher of the study found that the relationship between deaths from breast cancer and excessive weight only occur in estrogen receptor-positive forms of the illnesses. An estrogen receptor-positive form of cancer means the hormone ‘estrogen’ stimulates the progression of the disease.

Christina Dieli-Conwright, lead author of the study and assistant research professor at Duarte, California said in a press release that the relationship may depend on whether the breast cancer is dependent on the hormone.

The research showed that breast cancer patients who are overweight or obese tend to have increased estrogen levels in their blood, which could make out the reason why there is an increased risk of mortality.

The study is composed of 3,995 women who had an invasive form of breast cancer from the year of 1995 to 2006. Of those women, 262 had died from the disease.

Researchers examined their BMI or body mass index, which is a measure of an individual’s height and weight, when the patients were 18-years-old and at the time the patients were diagnosed. In this case, a BMI of 30 and more is classified as obesity while a BMI of 25 to 29 is classified as overweight.

Patients who were obese at the time they were diagnosed had an increased risk of dying up to 69 percent than those who were diagnosed at a healthy weight. An equal risk is given to those patients who were overweight at the time they were 18 years-old.

However, since the study was introduced at a medical meeting, the findings are still viewed as initial up to the time the study is published in a journal.