Hello,
I have only been doing this diet consistently for the last four or so months so I'm not an expert. However I did read somewhere online, perhaps at the Atkins website, that it could take as long as 2-3 months to start going down. I think most people see it go down within 6 weeks though. Also when you first start with the low carb diets your cholesterol will probably go up for a short time. I remember reading in my Atkins book that some people have to do a modified version of the diet to lower thier cholosterol because they are fat sensitive.
I am sorry that I can't give you direct quotes as I have loaned out my book.

Take care,
Lisa
Elisabeth Tilton