A recent study suggests that packing a fuller lunch bag may reduce certain types of breast cancer risk, Harvard Medical School (HMS) announced Tuesday.

The report, published in the Nov. 27 Archives of Internal Medicine and headed by Karin B. Michels, associate professor of obstetrics, gynecology, and reproductive biology at HMS and Brigham and Women’s Hospital, explored the link between body mass index (BMI) and premenopausal breast cancer.

“Premenopausal breast cancer is usually more aggressive and deadly than postmenopausal breast cancer,” Michels wrote in an e-mail. “It is also particularly tragic for a young woman to get breast cancer.”

Michels and her colleagues examined over 113,000 participants from 1989 to 2003 and found that a higher index correlated with a lower probability of premenopausal breast cancer.

According to the study, women with a BMI of 30 or above are 19 percent less likely to suffer premenopausal breast cancer than those with a BMI between 20 and 22.2, a range the Centers for Disease Control and Prevention classifies as normal.

The findings also show that an individual’s BMI at age 18 is the strongest indicator of a lower risk of premenopausal breast cancer.

“This provides further evidence that breast cancer originates early in life, in childhood or even earlier,” wrote Michels.

However, 18-year-old students should not use this relationship to usher in an Annenberg-induced freshman 15.

Being overweight is still a “very strong risk factor for postmenopausal breast cancer,” wrote Michels, adding that “the incidence of breast cancer increases with age.”

Michels emphasizes that her findings open new “research avenues” rather than advise on preventative health measures for women.

Until the complexities are explored further, the harms of obesity still outweigh any benefits.

Michels just received a grant from the National Institute of Health to continue studying what she terms “the mechanisms underlying this puzzling association.”