If your diet is not already clean, and you're not used to eating five or six smaller meals spread out over the day, it will be a lot to get used to. You can easily burn 6-700 calories in a workout. But you'll want to cut your calories and eat very smart and healthy. If you consider that you need to have a calorie deficit of about 3,500 compared to what your body needs in order to lose a pound, you can burn 500 calories and cut 500 calories in a day, and that will give you about a two pound loss for the week, which is a good goal. But you only have to worry about the workout for an hour a day. You have to worry about your diet ALL DAY.
The good part, as I mentioned above, is that there is no fad here. You have a tonne of flexibility as far as what you can eat, and as long as you cut out junk like soda, junk snacks, burgers, pizza, etc. you should the pounds drop off very quickly. I didn't even think I had 20 pounds to lose, yet I had lost 20 pounds in 60 days.
But the workouts make you want to eat better, the healthy diet makes you want to workout more, and when you start seeing real results (which you will very quickly if you follow the system religiously), that will motivate you even more.
Really, I cannot speak highly enough about this program if you're willing to commit to it.
There is no gimmick here: you have to work hard and diet hard (although "diet" just means eat smart and healthy, not follow some bullshit fad). The main benefit of the program for me was that it provided variety, structure, and intensity levels that I didn't have to think about.
I would HIGHLY recommend it.
One note: if you are WAY out of shape, start with a more basic program to get you up to speed. This isn't a program for people who are way overweight or haven't worked out in years. It is not for beginners.