Weight Watchers shares have gained after naming DJ Khaled as its new social media ambassador.
The American music producer will be documenting his weight loss on his social media channels.
Khaled Mohamed Khaled, better known as DJ Khaled, tweeted that he's "down 20 pounds and ready for more".
The 42-year-old platinum-selling artist has a large social media presence, including nearly 9 million Instagram followers.
"To be great is to be healthy; to be healthy means a shift in my lifestyle, and the new WW Freestyle program is all about healthier habits for my life," DJ Khaled said.
PART 5. 🔑🔑 MAJOR KEY ALERT!!! 🔑🔑 In full 2018 mode...excited to be living this #WWFreestyle life with you. Down 20 pounds and ready for more. Come with me on my journey to greatness. Bless up Weight Watchers!!! #2018secured @WeightWatchers pic.twitter.com/xaKHpzX5cv— DJ KHALED (@djkhaled) January 1, 2018
Mindy Grossman, Weight Watchers' chief executive, said: "By capturing and sharing his process, he will enliven and inspire his community, showing that it's possible to integrate healthy habits into your life."
Speaking to Afternoon Edition on BBC 5 Live, independent registered nutritionist Mel Blackman said: "He is going to bring attention from all sorts of different social groups, both from young girls and young males, admiring him and wanting to be like him.
"Traditionally dieting has always been aimed at females but with more anxiety around our personal appearance I think it's quite an opportunistic target to bring him on board," she added.
Oprah Winfrey, the former talk show host who appears in Weight Watchers advertisements, tweeted her support for DJ Khaled's appointment, saying "Can't wait to see you #blessup this program."
Ms Winfrey bought a 10% stake in Weight Watchers in 2015 when the company's shares were trading at about $7. They closed 8% higher at $47.83 in New York on Tuesday.
In November the firm reported better than expected profits and raised its outlook after reporting continued growth in subscriptions.
About 1.1 million members attend some 32,000 Weight Watchers meetings globally each week.
Financial terms of the deal with DJ Khaled were not disclosed.