According to recent studies, there appears to be little difference between the weight loss and the changes in fat and lean mass in cardio done in fasted and fed states. You may burn more fat during the session itself; however, this does not mean that you lose more fat in the long run. Whether one is fasting or feeding has less significance than the net energy balance. However, for competitive physique athletes looking to achieve super low levels of body fat, the question is open and protein sparing cardio may be effective in select advanced scenarios.