A diet low in fat may increase survival rates in women diagnosed with a particular type of early stage breast cancer, a study suggests.

Women diagnosed with what it termed estrogen receptor-negative (ER-negative) breast cancer who followed a low-fat diet for 5 years following their diagnosis showed a 36 percent reduction in their risk of dying from any cause for 15 years, the researchers say.

Women suffering from both ER-negative and progesterone-receptor negative (PR-negative) forms of breast cancer who followed the low-diet showed an even greater reduction in the death risk over the same time span with a risk of dying from any cause reduced by 56 percent, says study researcher Dr. Rowan Chlebowski, a medical oncologist at the Los Angeles Biomedical Research Institute at the Harbor-UCLA Medical Center.

The study involved more than 2,400 women ages 48 to 79 who all had some form of early stage breast cancer and had been treated between 1994 and 2001.

Half the women in the study were put on low-fat diets and given nutritional counseling, while the other "control" half were not counseled or advised to consider a diet low in fat.

Those on the low-fat diet reduced their intake of fat in their diets from an average 29 percent to 20 percent.

If all types of breast cancer were considered the death rate found in the low-fat group was 14 percent versus 17 percent in the control group, a difference not considered statistically significant, the researchers noted.

However, in the subgroup of women diagnosed with cancers that were hormone-unrelated -- ER-negative or ER- and PR-negative disease -- a much for favorable result was noted.

It is unclear exactly why a low-fat diet helped, the researchers acknowledged, but they suggest it could be due to the diet and its attendant weight loss reducing inflammation, which is known to affect cancer growth.

It's also unclear at this point why a low-fat diet would yield greater benefits in women with estrogen receptor-negative cancers as compared to those with estrogen receptor-positive cancers, Chlebowski said.

Experts did say the study findings suggest that a reduction in dietary fat represents a relatively easy and simple way of possibly reducing risks of premature death for women diagnosed with breast cancer.

"We're not talking about using some really expensive drug or really toxic therapy," says Dr. Anees Chagpar of the Yale School of Medicine, who reviewed the findings.