It is not possible to burn fat only on your arms, no matter how many push-ups you do. However, if you are already exercising and eating the right foods, you will lose fat all over your body, arms included. Push-ups are a compound body-weight exercise that help you build muscle on your arms, stomach and chest, which, when combined with fat-burning techniques, makes them appear less flabby and more toned. The key is doing push-ups regularly and correctly. Otherwise, you do not build the muscle you need to change your arms' appearance.