The P90X home fitness program has a star-studded fan list, and the results achieved by people who have adhered to it cannot be denied. But the system is far from being revolutionary, and is instead based on two simple premises: a strict diet and aggressive cross-training.

The intensive program, which is touted in late-night infomercials, is sold on DVD for about $120 through Beachbody's website. The man behind the program is Tony Horton, a trim bodybuilder who has served as personal trainer for celebrities such as Usher, Ewan McGregor, Annie Lennox, Billy Idol, Tom Petty, Bruce Springsteen and Stevie Nicks.

Horton explains the proper way to approach nutrition, intense cardiovascular exercises and light weightlifting in the P90X DVDs, but will this help people get fit?

Anyone who has the self-control to cut carbohydrates way down in their diet can lose weight on their own. Anyone who is willing to set aside the time to variously lift weights, do situps and pullups, and jump rope will tone their body. And the people who have both of those traits but need someone to guide them--even someone on their TV screen--would benefit from the P90x program.

Cross training (alternating between workout activities) works because it confuses the muscle groups, preventing them from building up to a certain level then plateauing without additional improvement. Jumping rope one day then lifting weights the next, and so on, keeps the body improving in different muscle groups, instead of focusing on one area and one kind of exertion.

Eliminating carbs and fats within a healthy diet will take pounds off, assuming portion size is controlled.

So what's so revolutionary?

Trainers love to give negative reviews of P90X, saying it's not that special, said Carl Daikeler, CEO of Beachbody, told the New York Times. They are right. It's not that special.

But it works.

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