As the other ladies have said, it's best to let your body rest until your 6 week check up. A lot of what you may think is baby fat could be bloating or the fact that your uterus has not completely shrunk yet. During the first 6 weeks postpartum it's necessary to let your body recover and not do anything too strenuous.
Usually after your 6 week postpartum check up. Even then my midwife said nothing too vigorous for a few more weeks.
i believe generally after you given a clear at your 6 week check up