I work out on a regular basis, and this DVD challenged me far beyond what I had been doing- and I started with the beginner level! The workout may only be 20 minutes, but it will be the longest 20 minutes of your life. This is an excellent fitness tool for people who are often pressed for time and are looking for a quick workout, such as on a lunch break from work. My one caution is that if you are not in shape or haven't worked out in awhile, you may get frustrated as this is VERY intense and may be beyond your ability at the moment. If you're looking for a challenge, then this is for you! I don't know about 20 pounds in 30 days, but I lost 5 pounds in a week just from doing this workout 3 times a week!