Kratos said:
- You're right, you are skinny, all the more reason not to do P90X, where one of the main goals is to lose weight.
From this statement it is obvious that you are not familiar with the program. The first sentence of the P90X fitness guide states "This program is for YOU, if you have acheived a respectable level of fitness.*" It continues to state "*If you're unsure whether or not you are in good enough condition to take on this extreme fitness program, see the minimum suggested requirements in the Fit Test section of this guidebook."
Here's the breakdown of the Fit Test requirements for men:
Pull-ups - 3
Vertical leap - 5 inches
Push-ups - 15
Toe Touch - at least 6 inches from your toes
Wall squat - hold for one minute
Bicep Curls - minimum 10 w/ 20 lbs
In and outs - 25
Jumping jacks - 2 minutes nonstop
These are by no means extraordinary or difficult, but they want to make sure you are in some semblance of shape prior to starting.
I have P90X and I have completed half of it. I found it great for all-around strength, flexibility, and endurance. I felt I needed to supplement it with a running regime as well, but other than that it was what I was looking for. As for your mention of using only body weight exercises and light dumbbells, that isn't entirely correct. Yes, there are a lot of body weight exercises, but they don't suggest to use only "light" dumbbells either. They stress to use the weight that will ensure you're last reps are difficult and to steadily increase weights. I'm 6'1" and 230 lbs and I have no desire to become "bigger", just stronger and with more endurance. I think everyone's definition of stronger is different as well. Maybe for you stronger means being able to benchpress 400 lbs and squat 1000 lbs. For me, stronger means that I can complete 50 push-ups with relative ease, 20 pull-ups, and be able to haul butt up flights of stairs with a weighted ruck on.