This sounds like the kind of diet that the person will immediately gain the weight back right after stopping
I started on the HCG diet last August. I stopped in April & have been off for the past few months. From my signature below, you can see that I lost 65 pounds - pretty significant for anyone. I'm 5'6 and have a very small frame, so it was major for me.
After being off the plan since April & really enjoying my summer with my girls both being home

, I've gained back 7 lbs. In an ideal world, I suppose I wouldn't have gained ANY back, but I am quite pleased overall.
I've done NutriSystem, Weight Watchers, Jenny Craig, Weight Watchers, a registered dietician's supervised plan, Weight Watchers, and now - HCG. HCG is the only plan where I felt satisfied & healthy throughout my program.
I did add some exercise (mostly walking), but I have a bum ankle & some pretty severe back problems - so the exercise was light. I also had a cardiac ablation procedure last March for an irregular heartbeat (congenital).
I was monitored weekly while on HCG (I used the sublingual drops) and am extremely thrilled with how well it worked for me. I plan to start back later this week to take off my "summer vacation" 7 lbs. & finish getting to my goal weight.
HCG may not be for everyone & there are some "questionable" people out there who have "hawked" modified versions of the original plan, but it definitely worked for me better than anything I have ever tried before - and I have spent about 17 years trying to get this extra weight off!
PS - I did this with 3 close friends and we all lost over 40 lbs.
