The P90X Lean program is a great option for anyone beginning P90X who wants to focus a little more on a lean physique, as opposed to a slighthly heavier focus on resistance training. It's a good choice for men and women both. Women in particular seem to be concerned about building up too MUCH muscle (I don't want to look like a weight lifter/too butch/whatever), so they may choose Lean. Know that the amount of work you have to put in to build up enough muscle to look too butch is probably more than what you will be able to achieve in one round of P90X, so if that's your concern, P90X Classic would probably be just fine.
That being said, Lean appeals to many because in a nutshell, there's less resistance training and more cardio and core-based workouts than in P90X Classic. It may also be a good choice for someone concerned about their knees, as the P90X Lean program doesn't include the Plyometrics workout (which is almost all jumping). Don't worry, P90X lean is still a TON of good sweaty work - I did the Lean program my first round of P90X and lost 25 pounds.
Just as in P90X Classic, P90X Lean is divided into three phases over the course of 90 days (13 weeks). The first three weeks of any given phase is a balance of Core Synergistics, cardio, Kenpo (cardio/kickboxing), an upper body and then a lower body workout, and yoga. You'll also do the 16-minute Ab Ripper X routine twice a week. The 4th week is a Recovery week, where you're still working hard, but don't do any resistance workouts.
Phases 1, 2 and 3 of P90X Lean are similar, but use different resistance workouts. Perhaps the best thing is to view the P90X Lean schedule to see how it all breaks down.
One thing I really liked about P90X Lean was the focus on Core. You do the Core Synergistics workout more often than in P90X Classic, and for me, building up that core helped my lower back not be so tired by the end of the day (I stand up most of the day chasing after my kiddos) and I feel like helped provide a stronger platform as a base for the other kinds of exercises.That lower back strength has been key for me, having a sore/tired lower back not be an issue is huge.
Overall I feel lean and mean, strong in the core, but still have added muscle that I've never had before - for me, most noticeably in my arms. I recommend the P90X Lean program as a well-balanced way to lose weight, tone up, and get in the best shape of your life! Go here to find out what P90X equipment you need to get started. You might also like these tips on doing P90X that are applicable to Lean, but appear in the article about P90X Classic before you get started.