Hi Jean,
I'm gpoing to go against the popular opinion here on this forum and tell you from experience that you need to get your body fat percentage at least in the 20's before you embark on a lifting program like STS or P90X that incoporates heavy weights IF YOUR GOAL IS SIGNIFICANT FAT LOSS.
I know, I know, everyone is going to argue that you need, must, should lift weights to speed metabolism and help carve out lean muscle mass. But I couldn't disagree more. I believe that light weights and high reps may help but it is always a caloric deficit that promotes fat loss to a significant degree.
Perhaps some of people that sing the praises of heavy weights for fat loss are already at an average BF%. But if you are 30% BF or above I would focus on a consistent caloric deficit that mathematically results in fat (weight) loss if that is truly your goal. Light weights and high reps helped me tone up but I didn't see the significant results I wanted until I got serious about the nutritional component, the caloric deficit.
Just my opinion. Lost 12 pounds since December with Fresstyle-like, no weight lower body workouts and 1400 calories/day. I had been doing various heavy weight programs previous to this. I haven't lifted a heavy weight in 4 months and have seen the best results for fat loss.
However, I can't wait for the day that I am ready for STS...probably another 15 pounds.
X
Not only will more muscle help bump up your metabolism, but it will also help you "tone" up since muscle takes up less space than body fat. Doing less cardio and more weight training is what actually helped me lose some weight last year!