A growing body of evidence suggests diet drinks might not be so slimming after all.

Advertising campaigns behind diet drinks from Coca-Cola, Pepsi and Dr. Pepper have long promoted the idea that consumers are taking the healthier, more weight-conscious option when it comes to choosing their favorite sodas. Diet Coke emphasized its drink has “no sugar, no calories.” Diet Pepsi tried launching its slender “skinny” can only a handful of years ago. And Diet Dr. Pepper’s “Lil Sweet” mascot is no subtle nod to the product’s supposed ability to shrink those who drink it.

But this past October, six lawsuits were filed in federal courts in New York and California arguing that the makers of Coca-Cola, Pepsi and Dr. Pepper are engaging in misleading and unlawful marketing practices of their diet beverages, as these drinks contain ingredients that raise the risk not only of weight gain, but of developing serious health problems.

“Some great injunctive relief would be if they would just remove the letter ‘t’ from the word diet,” said Abraham Melamed, one of the attorneys working on the three suits filed in New York, who added that branding these drinks as “diet” is “fraudulent, illegal, improper and needs to stop.”

AlterNet contacted all three beverage companies involved in the lawsuits. While none of the companies responded directly, Lauren Kane, a spokeswoman for the American Beverage Association, which represents the U.S. non-alcoholic beverage industry, wrote in an email that the “diet beverages that contain zero or barely any calories at all have repeatedly been shown to help people manage their diets. That is why we proudly stand by our products against these meritless legal claims.”