As weight-loss companies continue to spend millions on celebrity endorsers, ET dives into the $40 billion a year industry to see who's winning and who's losing.
Marie Osmond, Jessica Simpson and Jennifer Hudson are just a few of the celebrities who have been paid big bucks to endorse products for losing weight, but does their attachment to the brand actually make a difference?
PICS: Actors' Body Transformations For Roles
When Weight Watchers shifted course, taking celebs like Jessica and Jennifer out of their marketing plan, profits reportedly took a dip.
"The average person doesn't necessarily know which celebrity belongs to which program, which is something that can be troubling for companies when they hire celebrity endorsers," Sara Germano of The Wall Street Journal told ET. "But now there are so many different places to get information about weight loss and fitness that it's not just the celebrity speaking to you. The message is far more diluted."
Weight Watchers declined to comment.
For Nutrisystem, celebrities are a big part of their business -- and that doesn't seem to be changing any time soon.
"Celebrity relationships are definitely worth what we pay for them," Nutrisystem President and CEO Dawn Zier argued. "Our celebrities are authentic and true to our brand we choose them very carefully. With brand ambassadors like Marie Osmond who's lost the weight and kept it off, she looks fantastic and Dan Marino who put men's dieting on the map, we've done very well and we're very proud of our relationships. We're very happy with our celebrity relationships. In fact, I'd say they're priceless."
NEWS: Kirstie Alley Shows Off 50-Pound Weight Loss
Nutrisystem, who touts Marie Osmond as a spokeswoman, reportedly has seen membership increase by 13 percent while Weight Watchers struggles.
The real winners could be the stars themselves who stand to see a substantial profit. Valerie Bertinelli saw a resurgence in her career after showing off her bikini body in a Jenny Craig ad. Kirstie Alley parted ways with Jenny Craig in 2007 after three years, but the actress was brought back into the fold last year when Jenny Craig bought the weight-loss company Kirstie started -- Organic Liaison.
"Our sights were trained entirely on Kirstie Alley," Jenny Craig's Chief Marketing Officer Mike Raymond said. "We wanted Kirstie Alley and we got Kirstie Alley and we're thrilled with that."
NEWS: 6 Male Stars Who Lost a Shocking Amount of Weight
While the celebrity strategy continues to be popular, according to Germano, companies would be wise to retool for adapting to the digital age.
"The smart money is to place investment on making sure you have apps and ways for consumers to use your fitness product on the Internet," she said.