Taipei: Severely obese women who undergo bariatric surgery early may have a 20 percent lower risk of developing breast cancer than those who do not undergo the weight-loss procedure, according to a study led by physicians at Taipei Tzu Chi Hospital. The study found that women who underwent sleeve gastrectomy within six months of their first severe obesity diagnosis had a 20 percent lower five-year breast cancer risk than those who did not undergo surgery.

According to Focus Taiwan, Chong Kian-Hwee, an attending physician in the hospital's Department of Surgery, explained that while previous studies have shown bariatric surgery can reduce breast cancer incidence, this study uniquely examines the timing of the surgery. Chong and his team used data from TriNetX, a global health research network, analyzing patient records from 19 countries across Europe, the Americas, and Asia. They initially identified around 4 million women with a body mass index (BMI) above 35, considered severe obesity.

Patients who underwent sleeve gastrectomy were divided into three groups based on the timing of their surgery and were compared with a nonsurgical control group matched for age, diabetes, and hypertension. The study found that surgery within six months was associated with a 20 percent reduction in breast cancer risk, while no significant reduction was observed for surgeries performed six to 12 months later. Additionally, women who had surgery one to three years after diagnosis had a higher breast cancer incidence than those who did not undergo surgery.

The researchers noted that this does not necessarily mean delayed surgery increases cancer risk, as these women may have had more healthcare visits, increasing the likelihood of cancer detection. Chong emphasized that early surgery patients might be "more proactive" about their health, and long-term obesity can lead to metabolic abnormalities and chronic inflammation, contributing to breast cancer development.

Chong believes the findings can be applied to Taiwanese and other Asian populations, given the known links between severe obesity, chronic inflammation, and metabolic disorders. The research has influenced Chong's clinical practice, as he now discusses bariatric surgery benefits, risks, and potential complications earlier with patients having a BMI above 35.

Breast cancer is the most commonly diagnosed cancer among women in Taiwan, with 3,116 deaths in 2025, making it the second-leading cause of cancer death after lung cancer, according to the Ministry of Health and Welfare. The Health Promotion Administration reported in March that 51.3 percent of adults in Taiwan were overweight or obese. The study was published online in June in The Breast, an international peer-reviewed medical journal.