Adele is already rocking 2020 with a svelte new shape, a transformation that one fitness expert believes is credited as much as “90 percent” to dieting. The 15-time Grammy winner is rumored to have lost almost 50 pounds due in part to the sirtfood diet, which famously allows weight watchers to enjoy red wine and dark chocolate.

Los Angeles-based trainer Camila Goodis claims to have connected with Adele through a mutual friend, U.K. “X Factor” judge Ayda Field, and she alleges that the singer slimmed down with the trendy weight loss plan.

“I trained Ayda for a long time and it happens that they are good friends, so I did Adele when she was there in Robbie [Williams’] house,” Goodis told The Sun in an interview published Wednesday.

Adele shows off her dramatic weight loss while pictured with Harry Styles and James Corden on holiday together in Anguilla. (Joe Brown/BackGrid)

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“I don’t believe [Adele] liked exercise much but she has changed her lifestyle and I believe that 90 percent was dieting,” she continued. “Giving up processed food, sugar, soda and get into an exercise routine, like cardio and strength training, will change people’s [bodies.]”

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According to the New York Post, the 31-year-old songstress has shed nearly 50 pounds after hiring a fitness trainer and following the sirtfood diet.

As for the regime itself, the sirtfood diet emphasizes sirtuins, which are proteins involved in cellular health and metabolism. Sirtuin-rich foods include kale, arugula, buckwheat, chilies, walnuts and Medjool dates, as well as coffee, green tea, matcha, red wine and dark chocolate, Shape reports.

Nutritionists Aidan Goggins and Glen Matten first published the “The Sirtfood Diet” book in the U.K. in 2016, claiming that eating sirtuin-rich foods boosts energy and helps activate the so-called “skinny gene” through calorie restriction.

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Adele at the 59th Grammy Awards in February 2017. (AP)

Adele is said to have previously embraced the plan to slim down in 2016, while Pippa Middleton is also reportedly a fan, the Post claims.

A representative for Adele declined to offer further comment on the reports.

The British songstress recently made headlines when she was photographed soaking up the sun in Anguilla alongside pals Harry Styles and James Corden.

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Photos of the 31-year-old and her svelte shape quickly circulated on social media, receiving overwhelming praise from fans.

However, some critics expressed their disappointment that Adele was trending on social media for her weight loss, not for releasing a new album. The singer’s last record, titled “25,” was released in 2015.

Her transformation comes on the heels of her divorce in September from husband Simon Konecki after three years of marriage. They share a 7-year-old son, Angelo.

Fox News’ Stephanie Nolasco contributed to this report.