Another shot was fired in the heavyweight battle of the bulge-busters when the diet company Weight Watchers this week filed a lawsuit against one of its top competitors, Jenny Craig, calling its ads misleading.
Those weight loss ads are just about everywhere you look these days, featuring skinny celebrities like Valerie Bertinelli, Marie Osmond and Jenny McCarthy, pitching skinny bodies.
Weight loss is a $40 billion industry in the U.S., and the new Jenny Craig ad has the two weight loss giants squaring off.
Jenny Craig's ad featuring Bertinelli claims its weight loss program is more than twice as effective as its main rival.
"Jenny's delicious cuisine and the support of your personal consultant make all the difference, "Bertinelli, who lost 49 pounds on Jenny Craig, says in the commercial. "Jenny Craig clients lost, on average, over twice as much weight as those on the largest weight loss program."
Those claims have Weight Watchers fighting mad. The company says Jenny Craig's so-called science is a big fat lie.
"The claims that they are using in that advertising was just patently deceptive," said David Kirchhoff, the president of Weight Watchers International.
And now Weight Watchers is taking the fight to court.
"They compared a study they did this year, for one purpose, to a study we did 10 years ago," Kirchhoff said.
The Jenny Craig ads never mention Weight Watchers by name, but Kirchhoff says "everybody knew. You say the world's leading weight loss company; everybody knows who you are talking about."
Jenny Craig stands behind its message, and their science.
"We believe that when the court finally hears all of the evidence and our record is fully developed that the court will side with us and agree with us that our advertising claims are truthful," Lewis Rose, Jenny Craig's attorney and a partner at Kelley, Drye and Warren, said.
"GMA" showed the ad to obesity expert Dr. Louis Aronne, from New York Presbyterian hospital.
"I think that Weight Watchers has a point," he said. "You can't compare studies that were done in different locations at different times using different groups of people."
While the two companies slug it out, a federal judge has issued a temporary restraining order halting Jenny Craig from showing the ad, a fairly unusual development in a commercial libel suit.
As the case progresses the two crucial questions will be whether the ad claim is false, or misleading to the point of being the functional equivalent of false, and whether or not an ordinary person would be impacted by the ad's claims.
Jenny Craig's CEO issued a statement to ABC News that said, "We do not believe a head-to-head challenge is required to prove the effectiveness of the Jenny Craig weight loss program."
But Kirchhoff disagrees.
"I can understand how having rigorous clinical practices might be inconvenient for the marketing department at Jenny Craig, but nonetheless, most of us who do things the right way and with the right set of standards, would actually go through the trouble of doing it," he said.
In reality, the two weight-loss programs are very different. Weight Watchers' business relies on selling the philosophy of lifestyle change, a points system and group support. Jenny Craig's bread and butter is the sales of its packaged meals and personal consultants.
"The fact is you've got to find the program that works best for you," Aronne said.