The classic. Or, I mean, if you think weight is weight, then you can do loads of unhealthy things to your body and lose tons of weight. But losing fat? Lifting weights is one of the best ways to lose fat. Combine that with the cardio training in P90X, or my favourite, HIIT, and you'll be on the healthiest way to lose fat, increase strength and improve your overall health you can be. Remember that it's not healthy to lose more than 2-3 lbs a week. Lean is really meant for the long distance sport kind of guy, that doesn't want to increase muscle mass, because it'll be detrimental to his performance.
The double is for the insanely trained crowd. If you stress your body too much by not eating enough and/or exercising too much, your body will start counter-acting the fat-loss by having a steady stream of cortisol, which will be a huge hit for the motivation. Eat enough, work out, but not too much (especially don't do too much cardio - HIIT is optimal for fat-loss while avoiding excess cortisol and other negative effects from hitting the catabolic state you do when you run for a long time), and get a life-style you can stay with, and that's the way you'll stay forever healthy, and not be fit for two months, then bounce right back to the couch and the candy.