Women who are overweight or obese as they age or who consistently gain weight throughout adulthood face a significantly higher risk of developing breast cancer and uterine cancer, according to a recently published study in Cancer Epidemiology.
Researchers followed over 3.7 million Korean women for up to 12 years. All were cancer-free at the start and had taken part in national health exams, which included weight and height checks to calculate BM. The authors compared women’s weight status at two points in time, scientists looked at 25 different patterns of BMI change, ranging from staying at a normal weight to gaining or losing weight across different categories.
The results showed that women who were consistently overweight or obese, or who moved into a higher weight category over time, had a higher chance of developing breast or uterine cancer.
The authors observed that the risk was higher for women who had already gone through menopause. Women who went from being overweight to severely obese had more than four times the risk of developing uterine cancer compared to women who stayed at a normal weight. Furthermore, even women who lost a lot of weight, from overweight to underweight, also had higher risk, possibly due to underlying health issues that weren’t yet diagnosed.
For breast cancer, weight gain lead to an increased risk primarily in postmenopausal women. In contrast, among younger women who hadn’t gone through menopause, losing weight from a normal or overweight BMI was linked to a higher breast cancer risk. The reasons for this are not fully understood but may involve how body fat influences hormones like estrogen.
Smoking also seemed to play a role. Among women who never smoked, the pattern of risk was clear: more weight meant more risk. But among women who did smoke, the links between weight change and cancer were weaker or inconsistent. Researchers believe smoking may interfere with how body fat affects hormone levels, which in turn could influence cancer risk.
“In conclusion, persistent high BMI and further BMI gain were associated with increased risk of both cancers, particularly in postmenopausal women and never-smokers,” the authors wrote.
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