A descriptive study of individuals successful at long-term maintenance of substantial weight loss.
 

Denise Jack the cross-posting troll quoted:

The National Weight Control Registry (NWCR) is, to the best of our
knowledge, the largest study of individuals successful at long-term
maintenance of weight loss.

Their questionaires make it impossible to tell them you lost using a
low carb plan. Until they change that I suggest they are biased.
I don't suggest that their data is invalid, but I do suggest that they
decline to accept a large amount of valid data.