It works. I'm not sure you can go from total fat-ass to ripped in 12 weeks, but the basics of the program are sound.
You might also do some research on "CrossFit". Those are some absolutely brutal routines. They will get you fit fast.
But really, none of this is complicated:
- Exercise, hard, for half an hour a day. Combine resistance training and cardio.
- Eat lean meat and vegetables, particularly leafy greens.
- Incorporate some nuts and seeds into your diet.
- Don't eat starches. Don't eat bread, Don't eat sugar.
Do that, and you'll be fit soon enough.