Breast pain after gaining weight may be due to inappropriate clothing, breast hyperplasia, endocrine disorders, breast tumors. 1. Clothing discomfort: after gaining weight, the underwear and the clothes you usually wear may be too tight, which will lead to the breasts being excessively squeezed and rubbed, thus causing breast swelling and pain. 2. Mammary gland hyperplasia: Mammary gland hyperplasia is usually due to hormonal abnormalities in the patient’s body, obesity will lead to hormonal secretion disorders in the body to a certain extent, thus triggering mammary gland hyperplasia. Breast hyperplasia can cause breast pain, localized swelling and breast nodules and other symptoms. 3. Endocrine disorders: when stress or obesity can lead to endocrine disorders, causing breast swelling and pain, especially before menstruation, breast swelling and pain will be more obvious. 4. Breast tumors: Breast tumors can cause breast pain, lumps in the breast and nipple overflow and other symptoms, such as breast lipoma, breast fibroma and breast cancer. At the same time, mastitis, breast trauma can also appear breast swelling and pain. Careful differentiation is needed. There are many reasons for breast swelling and pain after obesity, and it is recommended that women should go to the hospital for timely examination and standardized treatment under the guidance of doctors when they experience abnormal weight gain and breast pain.