BREAST CANCER AND WEIGHT

I appreciate all the comments about the blogs last week and I invite you to invite your friends to participate.

We begin this week with a topic some don't like to consider, but we should because of its impact.  The numbers are so profound that we will make this blog short.

We have all been reading about the "obesity epidemic" and the negative effects of being overweight, but let's take a look and the science in two of the many article relating weight increase to breast cancer risk increase.

The first study, published in 2000 in Am J Epidemiol 152:514, is a pooled analysis of almost 350,000 US women using data from 7 prospective cohort studies.  Women who weighed at least 176 pounds (80kg) had a 25% higher risk of breast cancer than those women weighing less than 132 pounds (60kg).  The analysis was controlled for other factors.  Expressed as Body Mass Index (calculate yours at www.nhlbisupport.com/bmi/), women with a BMI >33kg/m2 had almost 30% excess cancer risk when compared to BMI <21kg/m2.

The next study is another report from the Nurses Health Study published in 2006 in JAMA 296:193.  Weight changes since menopause were followed in 50,000 US women for up to 24 years.  Among those not taking hormone replacement the results were very dramatic.  Those women who gained and kept on 22 pounds had an 18% higher risk of breast cancer than those who maintained their weight.  But even more exciting, those women who lost and kept off 22 pounds or more had a 57% lower risk of breast cancer than those maintaining their weight.  So, after menopause, each pound put on and kept on equals one percent more breast cancer risk, BUT for each pound taken off and kept off there is a two percent decrease in the breast cancer risk.  Twice the benefit for losing weight!

In future blogs we will look at potential reasons.  We are learning that some kinds of fat cells, particularly those gained after menopause are tiny "endocrine" factories secreting all kinds of substances, most of them harmful.