The sweet-peddling doc is suing the reality star, claiming Kardashian has been bashing his diet on Twitter.
In the lawsuit, filed in Miami-Dade, Siegal claims that when Kim called the diet "unhealthy" on her Twitter account, she was doing so out of "commercial motive" to promote her rival weightloss program, QuickTrim.
According to the lawsuit, Kradashian made "false statements on her Twitter page stating that Dr. Siegal is a liar and that Dr. Siegal's Cookie Diet weight-loss program is unhealthy."
Siegal, a South Florida weight loss physician who invented the six cookie a day diet over 30 years ago, is suing for unspecified damages.
It's not the first dust-up between Kardashian and the Cookie Doc. Just last week, Kardashian sent Siegal a letter threatening a lawsuit if Siegal didn't remove a link from his Website that implied Kim uses the diet.
The link has since been removed.