One diet I had success with in the past is called "Fit for Life," by Marilyn and Harvey Diamond. I don't remember the timetable exactly, but I lost seventy (70) pounds fairly easily over a period of about three months!
I didn't keep good track of my weight, so I'm not even sure of what my exact weight was before or after, just that I'd lost the equivalent of a small child. The fact that I didn't have a scale points up and to my having a weight problem in the first place.
The diet's main focus is digestion. They suggest that, because certain foods are digested by acid - protein - and others by alkaline - starch - that if you mix the two, you will have trouble losing weight.
I can't be sure of the exact mechanics of what happened - I just know I lost 70 pounds in a pretty short amount of time!
I tend to think it would work better if there was more weight to lose, rather than those last 20 pounds, but I could be wrong. For me, I definitely had more weight to lose, after having a baby, and also being a person who likes to feel full, up to several times a day.