Many women are anxious to start an exercise program after giving birth. Once your body has healed from childbirth (at least 8 weeks postpartum), there is no reason you cannot start a fitness program. Moderate exercise will not change the taste or quality of your breast milk. There has been some concern that the lactic acid that builds up during high-intensity physical activity could change the taste of breast milk. While this is possible, the change would only be minor, would be harmless to baby, and would only occur with very high levels of exercise - above the aerobic threshold. You need not worry about the quantity of your breast milk either. In fact, in some studies active mothers produced more breast milk than mothers who were not active!
If you want to start exercising there are some things you can do to make things easier and prevent possible problems. 
ill refuse the breast because they do not like the taste of the salt in your sweat. Starting an exercise program can be hard at first, but stick with it, it does get easier. Adopting an active, healthy lifestyle is one of the best things your can do for yourself and your baby!