Prevalence of breast cancer-related risk factors in underweight premenopausal women: the Korea National Health and Nutrition Examination Survey IV-VI.

Underweight Korean premenopausal women exhibit distinctive features associated with an increased risk of breast cancer, except for a lower rate of early menarche. These associations were prominent in recent generations. Assessment of the association between underweight and premenopausal breast cancer risk should focus on promoting healthy lifestyles to reduce breast cancer risk.