You know, I hate stories like this. It gives everyone the impression that *anyone* can lose 20 lbs in a month. Not true, only very obese people can lose _fat_ that quickly and remain healthy. There's a research paper I keep handy which basically says that the average maximum at loss rate for most people is about 0.9% of their fat per day. I'll round it up to make things simpler, so 1% of your fat mass (not weight, just fat) per day.
Note the mathematical consequences: The less fat you have, the more slowly you can get rid of it without losing lean mass. These "success stories" are generally nothing more than "I'm so fat I can eat nothing, drink only water *and* exercise enough to burn 3500 calories a day."