Kim Kardashian claims that some doctor who invented the “cookie diet” used her name to endorse the product without her permission. (source). She tweets that the diet is “unhealthy” and that Dr. Siegal is “lying.” So Siegal files a defamation suit against her.
The complaint is an example of pretty bad legal strategy. The plaintiff makes allegation after allegation about how famous he is — thus conceding that he is a public figure.
This is basic defamation 101 — a public figure has a much higher burden of proof than a private plaintiff. A private plaintiff only needs to prove that the statement was a false statement of fact that tended to damage his reputation. Truth is an affirmative defense to that action that the defendant has to prove. On the other hand, a public figure has to both prove that the statement is false, and has to prove that the defendant published the falsehood with knowledge of its falsity, or with reckless disregard for the truth. Public figures who prevail in defamation suits are about as rare as fad diets that are good for you.