Researchers assigned overweight subjects to three groups: diet-only, diet plus aerobics, diet plus aerobics plus weights.
The diet group lost 14.6 pounds of fat in 12 weeks. The aerobic group lost only one more pound than the diet group. Their training was three times a week starting at 30 minutes and progressing to 50 minutes over the 12 weeks. Nothing special.
But the weight training group lost 21.1 pounds of fat. That's 44% and 35% more than diet and aerobic-only groups respectively.
The addition of aerobic training didn't result in significant fat loss over dieting alone.
(Reference: Kramer, Volek et al. Med. Sci. Sports Exerc., Vol. 31, No. 9, pp. 1320-1329, 1999.)
There's obviously nothing wrong with doing cardio, but I feel most women tend to over do it while completely ignoring strength training.