Have you heard the news about the big payback for shedding just a little extra body baggage? Here’s the scoop: If you’re postmenopausal and overweight, dropping just 5% of your body weight—that’s a mere nine pounds if you currently weigh 180—can significantly reduce levels of hormones linked to breast cancer, a new study shows.

Background: Overweight and obese postmenopausal women are considered to be at elevated risk for breast cancer. That’s because, after menopause, fat tissue becomes a major source of various estrogens and other sex hormones that are implicated in tumor growth. Overweight women produce more of these sex hormones than thin women because they have more fat tissue.

For the new study, participants included 439 sedentary, overweight women ages 50 to 75. One group did 45 minutes of aerobic exercise, such as brisk walking, five days a week…a second group was assigned a diet of 1,200 to 2,000 calories a day…a third group followed both the diet and exercise regimens…the control group did not change their usual diet or exercise routines. Blood tests were done at the start and end of the study to measure levels of hormones linked with breast cancer risk.

After one year: In the control group, there was no change in weight, and hormone levels actually worsened…in the exercise-only group, weight loss and hormone reductions were very modest (though of course exercise has other health benefits). In contrast: Women in the diet-only group lost 11% of their body weight, on average, while those in the diet-plus-exercise group lost 12%. And in both groups, sex hormone blood levels dropped significantly—by 10% to as much as 26%, on average, depending on the hormone. Such changes, according to previous research, suggest about a 50% decrease in breast cancer risk. Generally, the greater the weight loss, the greater the improvement in hormone levels…yet even participants who lost just 5% of their body weight experienced hormone level changes suggestive of a 22% reduction in breast cancer risk, researchers said.

Bottom line: If you are overweight, start today to make the lifestyle changes that will take off some of those pounds. Besides all the other well-known benefits, slimming down a bit may help you avoid breast cancer!