Barbell bench press is mainly for anaerobic exercise of chest muscles. Anaerobic exercise can't help to reduce fat in a short time. If you want to lose weight, you should do aerobic exercise (that is, raise your heart rate and keep it at a high heart rate for more than 20 minutes). However, the muscles you exercise can raise the surrounding fat. For example, practicing chest muscles can prevent sagging chest fat and improve dressing style.