Any conditioning program will work, diet is the key, 70 percent diet, 20 percent working out and the other key 10 percent is proper rest. This is why things like P90X work for people. Get it, the key is the 90 part. If you can stick to 90 days of course you will see results. Most people quit their workout program after 2 weeks because they push themselves too hard to start and they don't see results immediately. Around 60 days you will see improvement but 90 days seems to be when the mirror changes. Now, programs like that stupid Insanity will work for a while but you cannot continue to beat down your body like that you will eventually give it up. Look at the bodybuilders, yes they use roids but they don't kill themselves for long periods in the gym, they hit it hard for short durations, the eat like champions, clean, clean, clean, then sleep so their body can grow.
Oh and lastly, that P90X puke about how they invented a revolutionary technique called "muscle confusion" is a joke. Bodybuilders have known this forever, however their is absolutely no way your body plateaus in 90 days. All changing it up does is keeps the week minded from getting board during this time frame. Didn't you notice P90X, Insanity and the original Beach Body spew is all from the same company. Its all about making great inspiring commercials to sell product.