For those of you concerned about the 500 calorie diet (which is not what I was on), you can search "HCG diet" and there is an entire protocol that goes along with the HCG shots.
I was on a modified HCG diet in which I did eat more than 500 calories a day - probably 1000 or so, but I was not counting calories. I was on more of an Atkins diet as I ate alot of protein and fiber. I also followed the low glycemic index list of foods. Reducing sugar was the main goal as well as keeping my muscles healthy.
Research any diet you attempt. At my clinic, I am followed by a real MD and only started this after seeing the results my MIL and SIL had. It is not cheap and I could buy the HCG shots via the internet, but I chose to be followed by a MD as I do have some health concerns that I am losing the weight for.
As far as Phentermine being legal cocaine, I was on it 3 months and I am nearing the end of a month off and I have not craved it or had alot of food cravings - this week has been kind of bad as it is my monthly time. I have been given a prescription for next month, but I am going to see how I do before I use it. As with any drug, it can be abused. Also, like a PP said I never got a jolt of energy from it - but I did only take a half pill a day.