Circut training is very useful if like yourself, one is trying to shed some body fat. It works well because you are basically giving your self a cardio workout during your weight traiing. However, you have to be careful with the word "significant."
But you can't really say if a traditional workout + cardio, or a curcuit style + cardio would be more effective. Clearly there are pro's and cons to both. For a "noob" to the gym world I would say they would most likely see greater results earlier on using a circut style, or using lots of supersets. But for someone with less Body fat to loose they would probably be better off using a traditional scheme(+cardio).
As with everything variety is important so switchig back and forth would probably help maximize results as well.
