Men with large chests may be caused by physiological factors such as obesity, and may also be caused by diseases such as male mammary gland dysplasia and breast tumors. 1. Obesity: If men often overeat, or gain weight in a short period of time, obesity may lead to an increase in breast fat, and the chest becomes larger, which is a physiological factor, not a disease, without special treatment. 2. Gynecomastia: Gynecomastia is a disease caused by the imbalance of the ratio of estrogen and androgen in male body, which leads to the abnormal proliferation and development of breast tissue, and is mainly manifested in the obvious proliferation and enlargement of breasts, and some of the patients are accompanied by the feeling of touching pain, therefore, the large breasts may be caused by this disease. 3. Breast tumor: Breast tumor is a kind of tumor that occurs in the breast, which mainly manifests as breast lumps, nipple and areola changes, nipple overflow and other symptoms, and the gradual increase of breast tumor may cause chest enlargement. It is suggested that patients should consult doctor for examination in time, carry out targeted treatment after clarifying the cause of the disease, pay attention to diet control and proper exercise in life, pay attention to the changes of the chest at the same time, and follow the doctor’s instructions for rechecking and so on.