Losing 10 pounds in early adulthood may help women with certain gene mutations avoid getting breast cancer at an early age.

The finding focuses on BRCA1 or BRCA2 gene mutations, which greatly raise breast cancer risk.

“The results from this study suggest that weight loss in early adult life (age 18 to 30) protects against early onset BRCA-associated breast cancers,” write Steven Narod, MD, PhD, and colleagues in Breast Cancer Research.

“Weight gain should also be avoided, particularly among BRCA1 mutation carriers who elect to have at least two [full-term] pregnancies,” they continue.

Narod is a professor in the University of Toronto’s public health sciences department. He also directs the Familial Breast Cancer Research Unit at the university’s Centre for Research in Women’s Health.

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About the Study

More than 2,000 women from five countries participated. All had BRCA1 or BRCA2 gene mutations. Those with breast cancer were compared with women of similar backgrounds without the disease.

The women filled out questionnaires about their weight at age 18, 30, and 40. Self-reports of weight from past years aren’t always accurate.

Some of the women reported fairly stable weight over the years. Others reported losing or gaining more than 10 pounds.

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Key Findings

—Breast cancer risk was 65 percent lower in women with the BRCA1 gene mutation who lost 10 pounds between ages 18 and 30, compared with those who didn’t lose or gain more than 10 pounds.

—Breast cancer risk was 44 percent higher in women with the BRCA1 gene mutation who had two full-term pregnancies and gained more than 10 pounds between ages 8 and 30, compared with women with relatively stable weight.

—Weight changes from age 30-40 didn’t affect the risk of getting breast cancer before or after menopause.

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Age Mattered

“The period between age 18 and 30 years appears to be a critical one when weight gain should be avoided in mutation carriers,” write the researchers.

How much weight did the women lose?

Women with the BRCA1 gene mutation who lost more than 10 pounds from age 18-30 reported weighing an average of 142 pounds at age 18 and losing nearly 19 pounds, on average, by age 30.

The study doesn’t say how the women lost weight. So, it’s not known if they exercised more, crash dieted, bounced up and down the scale, or permanently upgraded their eating habits.

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What About BRCA2?

In women with the BRCA2 gene mutation, weight loss in early adulthood brought “modest” protection, but the benefit was mainly seen in women with the BRCA1 mutation.

That finding should be checked in the future, write the researchers. They note that their study had a relatively small group of women with the BRCA2 gene mutation, which might make it harder to detect patterns in those women.

If you are considering losing weight or have questions about your breast cancer risk, consult your doctor.

A healthy lifestyle may also help reduce your risk of breast cancer. According to the Susan G. Komen Foundation these may help:

—Be physically active.

—Maintain a normal weight.

—Reduce the amount of “bad” fats (saturated and trans fats) in your diet, and eat foods that contain more “good” fats (polyunsaturated and monounsaturated fats, like olive and canola oil). Certain types of fat may contribute to increased risk of breast cancer and some can lower the risk.

—Take multivitamins with folic acid (often called folate on nutrition labels).

—Limit alcohol to less than a drink a day.

—Breastfeed instead of formula feed your infant if possible.

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By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Kotsopoulos, J. Breast Cancer Research, Aug. 19, 2005; vol 7: pp R833-R843. News release, BioMed Central.