You need to open your mind and broaden your horizon.

I've seen that study before. It is a little biased and it shows by the fact that I've heard of probation officers using this study to screw people in court who haven't smoked in 30 days but are testing positive.

I know first hand of several people who weren't fat who were under 30 and took nearly 60 days to get clean. Why, because they smoked high quality weed many times a day, not because they were fat and inactive.

You can look here and other forums and find people who aren't fat and inactive who take more than 30 days.