By definition fasted cardio is performing cardio when blood glucose/glycogen levels in the body are low. The theory is this causes an increase in lipolysis and fat oxidations rates to provide the body with energy. Some believe this leads to losses in body fat. A 2014 study conducted by Schoenfeld et al. disagrees. The researchers discovered body composition changes associated with fasted or unfasted cardio were similar regardless after four weeks of performing 1 hour of steady state cardio three times a week. For now, it seems fasted cardio does not work for fat loss.