Elliptical machines: effective or not?

I read an article saying that most people using elliptical machines are overweight and will stay overweight as long as they use this cardio method. Now that really shocked me -- big time! (If this statement holds true, that is.)

So the big question is WHY ISN'T IT AS EFFECTIVE AS THE OTHERS? Here's the answer the I got based on research.

"Because you just don't do as much mechanical work as you do when you run or cycle. Basically, it's just easier and less effective. Getting your heart rate up is not the key determinant of fat loss."