You've probably heard that your weight can impact your risk of breast cancer, but there's a more specific link that you should be aware of: putting weight on during middle age. Women who gain as little as two pounds a year during middle age (between 40-50 years old) have an increased risk of getting breast cancer before age 50, according to a new study in the International Journal of Cancer.
The researchers recruited more than 205,000 women from nine countries and weighed them twice—once at the beginning of the study, then again about four years later. For another seven and a half years, they tracked the rate of breast cancer among the women—and an interesting relationship emerged: The ladies in the "high weight gain" category (defined as gaining about two to 11 pounds per year) had a nine percent higher breast cancer risk.
This association was strongest when the researchers just looked at breast cancers diagnosed before or at age 50. And interestingly, losing weight was not associated with breast cancer risk in this study. (Although it should be noted that previous research shows that a high weight can increase your breast-cancer chances.)
So why might middle-age weight gain increase your risk of breast cancer? The researchers speculate that it's because of the pattern of weight gain among women in their mid- to late-forties and fifties: Fat tends to congregate around their belly. Past research has also suggested a link between waist size—an indicator of visceral fat, the most dangerous kind—and a risk of being diagnosed with breast cancer before menopause.