for those of you who combine weight training and cardio on the same day and the priority is weight loss,i would recommend that you start with the weight training first and then move to your cardio workout and half an hour of cardio would be enough,the reason,you would be using your stored energy to have a stronger and better weight training workout,this will deplate your stored energy and you will be left with your own fat to fuel your cardio workout,you see you will be using the right fuel for the task.