Gwyneth Paltrow may have stepped into some poop with her advice website Goop -- because a famed nutritionist says she ripped off his copyright in an article last month.

Gwyn, who generates thousands of clicks and dozens of snarky remarks with the self-help site, published a piece with a headline about "Diet Detective Kelly Dorfman," who wrote the item. Trouble is, Charles Platkin, who's written several books about good eating habits, says he owns the phrase "diet detective" and he wants Goop to cut him a check and stop using it to refer to Dorfman.

Platkin adds that his complaints to Paltrow's company “were all ignored and/or dismissed," and now he wants to tell his story to a jury.