After menopause, overweight women appear to have a higher risk of breast cancer than slender women. But before menopause, women who weigh more seem to have a lower risk of breast cancer. Researchers in California looked at a group of women to find out something slightly different: the risk of dying from breast cancer.

What the researchers wanted to know: What's the association between body weight and breast cancer death?

What they did: The researchers studied medical records for almost 1,500 women diagnosed with breast cancer at the Kaiser Permanente San Diego Medical Center in California. About two thirds of the women were diagnosed when they were 50 or older. The researchers were mostly looking at body weight at diagnosis and whether each woman had died of breast cancer, rather than dying of something else or still being alive.

What they found: If their cancer was diagnosed early, women were more likely to die from breast cancer if they were heavier—for example, women who weighed 175 pounds or more at diagnosis were more than twice as likely to die from their cancer than women who weighed 133 or less. That wasn't true of women whose cancer was more advanced when it was discovered—probably because those cancers are much more likely to be lethal, so being skinny may not help.

What the study means to you: There's no evidence that losing weight once you've been diagnosed with breast cancer improves your chances of survival, the authors write. But this study suggests that not being overweight in the first place helps.

Caveats: The researchers don't say why they used weight in their analysis instead of body mass index, a measure of weight that adjusts for height (a very short woman and a very tall woman can both weigh 150 pounds, but only one of them is obese).

Find out more: Read an excerpt of U.S. News editor Marc Silver's book Breast Cancer Husband

Read the article: Enger, S.M. et al. "Body Weight Correlates With Mortality in Early-Stage Breast Cancer." Archives of Surgery. September 2004, Vol. 139, pp. 954–960.

Abstract online: http://archsurg.ama-assn.org