- Coronavirus pandemic
image sourceGetty Imagesimage captionOprah Winfrey onstage during her 2020 Vision tour, sponsored by Weight Watchers International
Shares in WW International, formerly known as Weight Watchers, have dived 25% after the firm said people were putting diets on hold after lockdown.
The weight loss firm, which is backed by talk show host Oprah Winfrey, had 4.9 million subscribers at the end of June, down from 5 million last year.
Boss Mindy Grossman said part of this was a seasonal effect.
But she also said people are less worried about what they eat as they venture out of their homes again.
"While people are acknowledging their need for recommitting to weight loss and wellness, our recent consumer research shows that, at the moment, they're also asking for a pause to enjoy social reconnection," said Ms Grossman.
"With both traffic and search under pressure, this sentiment shift appears to be across the weight loss and wellness category."
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Like other dieting companies, the firm benefited during the pandemic as consumers stuck at home decided to get back into shape.
Many people had put on weight as they stopped commuting to work and increasingly turned to food and alcohol to manage stress.
However, in the three months to 30 June, subscriber numbers fell or were flat in all its key markets, including North America, the UK and the rest of Europe. Sales of its branded products slipped 6.9%.
Founded in 1963 in New York City, WW International provides a weight-management programme and food plan to subscribers.
Customers can participate through in-person group meetings or digitally. The firm also makes money out of branded goods and services such as magazines and snacks and drinks.
WW is well known for its high profile ambassadors who currently include Ms Winfrey, actress Kate Hudson and comedian James Corden.
Ms Winfrey bought a 10% stake in the company in 2015 and is a member of its corporate board.