Myka, Building lean muscle is the best way to increase your metabolism and burn fat. Don't be afraid of lifting weights, a program like P90x will not have you looking like a body builder I assure you. More Lean muscle = more calories burned throughout the day.

40 minutes is plenty of time to get a lot of work done. I have been using a program that is available online at http://www.getLEANin15.com Every week I get 5 new workouts for the week that are designed to workout your full body in the week. They are always different and in different orders so I'm not doing the same thing all the time. AND the best part is that the workouts are 15-20 minutes. It is a High Intensity Strength training Circuit. So you don't stop moving for the whole workout and burn a lot of calories while doing it. That also leaves me with 15-25 minutes to do a "cardio" interval on the treadmill or elliptical. But no matter what you choose I assure you, if you are working more efficiently you can get a phenominal workout in 40 minutes. It is a misconception that you need to spend long hours at the gym.