It's a great addition. Yoga tends to be more mussel building and toning your body, when working out to loose weight you need a good combination of cardio and body toning. I love doing Yoga and it's very helpful to me, but if I didn't walk/run on a treadmill I wouldn't have lost any weight.
This is not exactly the forum to be asking this question, but to answer it, the only way to lose weight is that "calories in" needs to be less than "calories out". So with eating less and exercising more you should reach this goal. No matter what fad diet you do, this is the basic strategy of all of them. Just make sure you don't do a dangerous diet that makes you eat less than 1200 calories in a day. The website looks like a fad diet and you don't have to spend extra money just to lose weight. Plus, once you are done with the program, does it really teach you how to eat right once its over?
For instance if you burn 2000 calories in a day, then to lose weight you need to eat less than this and burn calories with exercise. So you could eat 1500 calories in a day, plus exercise to reach that balance to lose weight. Of course it is different for each person so just try to eat healthy and cut out the snacks until you see the pounds roll off :D