For girls, chubbiness may protect against breast cancer later in life, a new French study suggests.
Women in the study who had larger bodies at puberty were less likely to develop breast cancer after menopause than women who were lean at puberty, the researchers said.
The results held regardless of the women's body sizes at other ages.
The findings may seem counterintuitive. After all, obesity is known to increase the risk of several cancers, including colon, kidney and esophageal cancer. And girls who are obese are more likely to begin their menstrual cycles at younger ages a risk factor for breast cancer.
However, the study adds to a growing body of research suggesting that some extra body fat in the pre-teen and early adolescent years actually reduces breast cancer risk .
Researchers still aren't sure why this is. It could be that, in overweight girls, the breast tissue is less dense , which may decrease breast cancer risk, said study researcher Guy Fagherazzi, at the Gustave Roussy Institute, a cancer research center in France. Or it may be that although overweight girls tend to begin menstruation early, they have irregular cycles, and so their risk is not what would be expected, Fagherazzi said.
Fagherazzi said the new study should spur additional research into the biological factors that are responsible for the link. The study was presented Nov. 3 at the annual meeting of the American Institute for Cancer Research in Washington, D.C.
Regardless of its impact on breast cancer risk, obesity is known to increase the risk of a number of ailments, including coronary heart disease, stroke, high blood pressure and diabetes, according to the National Cancer Institute.
The new study involved nearly 100,000 French women between the ages of 40 and 65. Participants were shown pictures of eight body shapes, ranging from lean to large, and were asked to choose which picture best represented them at different stages of life.
After 13 years, about 3,500 participants had developed breast cancer. Women who had the largest bodies at age 8 and at the onset of menstruation were 26 percent less likely to develop breast cancer after menopause compared with women with the smallest bodies at age 8 and at the onset of menstruation.
No association between body size and breast cancer risk was found at other ages.
The participants in the study were teachers or spouses of teachers, who tend to be more health- conscious than the general population, Fagherazzi said. For this reason, those with the largest body types in the study may not have been obese, but merely overweight.
A study in the general population, which would be expected to have a larger portion of obese people, might find a different result, Fagherazzi said.
Pass it on: Chubbiness at the onset of puberty in young girls may protect against breast cancer late in life.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.