because the calories you burn while doing cardio are comming from fat, the dextrose that you take in pwo will be utilized in the transportation of protein and nutrients to the muscles so your still burning fat and feeding muscles and you get a metabolic increase from the resistance training ... thats the point
you lift you burn 700+ calories not much fat though you run lightly for 20 burn 300 calories almost all fat you eat protein/dex thats about 450+ cals that are consumed from the 700burned from lifting still have happy muscles and calorie deficite for getting lean .. NEAT EH?