Follow General Motors diet chart... It reduces about 7 pounds in a week without any exercises. But if you do Tabata exercises (along with tabata music) and follow the diet, you'll be ripped by the end of 27th day. I can't follow it because that diet is too difficult for me.
The diet is the most important for such a short time to get results - cut starchy carbs, drink lots of water, increase protein intake and cut all processed foods. Basically eat fish or chicken and salads or steamed or raw veggies. No fruit. No breads or rice or pasta. No sugar or aspartame. Clean eating will get you 10 pounds in 4 weeks.
High Reps high sets only 1 minute max rest between. Keep your heart rate in the fat burning zone.
Water, water and water!