I've never found cardio exercise to be very helpful for decreasing body fat. I spent my college years and beyond as a runner, and reached a point where I was doing 3-6 miles almost every day. My aerobic capacity was good, but I didn't look the way I wanted to. In my early 30s I finally discovered strength training, and that changed everything. Now (I'm 37) I do very little cardio other than walking and gardening. I go to the gym 3x/week for a mixed workout of yoga-style stretching and weight training, and I've had terrific results for what feels to me like a minimal investment of time!
I really like the book "5-Factor Fitness" by Harley Pasternak. It's the latest in that wearisome trainer-to-the-stars category, but he actually does a good job of teaching you how to rev up your metabolism. The two biggies are 1) eat frequent small meals/snacks so that you never go hungry, because your body slows down calorie-burning when you don't eat, and 2) regular strength training! He shows you how to do it at home with one or two sets of hand weights, which is the only expense. No gym membership required.
From my experience and that of several other women I know, not much happens weight-wise for at least 6 weeks after you start strength training, though you might notice improved muscle tone. But then there's a point where your body seems to wake up and say, "Oh! Hey!" and kicks into a higher gear. That's when the inches start coming off.
Good luck! I'm "intending" success for you.
