Do you do your cardio in the same session you hit the weights? While that might be a logistical necessity for some, a study published in the journal Applied Physiology, Nutrition, And Metabolism examined what happened when you do the two workouts together and then separately. Finnish scientists examined three groups of subjects. The first two did cardio and weight training in the same workout, but switched the order, for a total of three training days a week.
The third group did the modalities on separate days and thus trained four to five times a week. After 24 weeks, all three groups made about the same gains in strength. However, the group who split up their cardio and iron session lost significantly more fat than the other groups. Endurance improved more in the separate group as well.