Asked her motto in an interview with fashion Web site WWD, Moss replied that one was "nothing tastes as good as skinny feels."
The same slogan is posted on Web sites encouraging girls not to eat.
Mary George of British eating-disorder charity Beat said Thursday that Moss's words were "very unfortunate."
She said, "comments like this make it even more difficult" for young people struggling with an eating disorder.
The 35-year-old Moss is famous for her waif-like look, which helped spur a trend for super-thin models in the 1990s.
Moss's spokespeople could not immediately be reached for comment.