Adele once confidently declared: "I'm not going to lose weight because someone tells me to. I make music to be a musician, not to be on the cover of Playboy."
So when she emerged after a three-year break to debut a significantly slimmed-down figure, it came as something of a surprise to fans who had loved her unapologetic pro plus-size stance.
The 27-year-old has remained coy about how she achieved her slender new frame - highlighted in a stunning cover shoot for Vogue magazine last week.
But The Sun on Sunday has revealed her dramatic new look is down to her no-nonsense personal trainer Pete Geracimo and the gruelling training regimes the singer has adopted to get fit for her new world tour.
Geracimo, an Australian former elite triathlete, introduced Adele to regimes that actually got her liking the gym.
The mother-of-one is thought to have lost at least 14kg after teaming up with the manager of swanky $12,200-a-year gym KX, in Kensington, West London.
He has got Adele to work out with weights (which she says she likes), a tough circuit regime called the Modified Strongman Workout and a punishing, high-intensity program called Tabata (which she says she really doesn't like).
Talking about his style of training, Geracimo has revealed: "Modified Strongman Workout is one of the fastest and most efficient ways of getting results. It trains a wide cross-section of muscle groups and is very effective in boosting your metabolism and fat burning."
Specialising in "transforming the average under-conditioned person into a healthier and cardio-fit machine", Geracimo's training techniques include circuits, high-intensity workouts, hill sprinting and working out in water.
Adele has repeatedly made clear her feelings about exercise. After sharing a hilarious black-and-white picture on social media of her looking miserable while in the middle of a weight-machine session, she has been blasé about her disdain for physical exercise.
She says she has hit the gym only to shape up for her 105-date world tour, and to be healthy for Angelo, her three-year-old son with charity boss Simon Konecki.
The superstar revealed: "I was trying to get some stamina for my tour so I lost a bit of weight.
"Now I can fit into normal, off-the-shelf clothes, which is really a big problem for me. It's to get in shape for myself, not to be like a size zero or anything like that.
"I mainly moan. I'm not skipping to the f***ing gym. I don't enjoy it. I do like doing weights, I don't like looking in the mirror. Blood vessels burst on my face really easily so I'm so conscious when I'm lifting weights not to let that happen. And if I don't tour, you'll catch me back down at the Chinese.
"I absolutely loved [smoking] but it's not that f***ing cool when I'm dying from a smoking-related illness and my kid is, like, devastated."
Adele is so close to Geracimo he joined her in New York during a press trip in November.
He posted a picture of a ticket to see Adele's Radio City Music Hall gig, writing: "Hello. Cannot wait to hear my girl sing!!"
When she burst back on to the scene with No. 1 single Hello in October last year he also posted a jokey Instagram message pretending he had 1000 missed calls from his eager-to-train client.
He captioned the photoshopped screengrab, showing she had tried to be in contact: "Had my phone on silent!!! Oops!!"
The pair previously trained together before Angelo was born in 2012.
While Adele was pregnant, he tweeted her: "We miss you at KX!"
On his Instagram recently the super-fit gym nut moaned about "obese" people, writing: "I think I just found one of the main reasons Californians are obese. Walked past this restaurant and it was like watching pigs at the trough!!! #sicktomystomach".
Adele has also started eating and drinking much more healthily.
She admitted she has "practically" given up booze and stopped having cups of tea overloaded with sugar.
In a recent interview she said: "I used to drink ten cups a day with two sugars in each so was on 20 sugars a day. Now I don't drink it and have more energy than ever."
She also has Pure Package deliver her nutritious, low-calorie meals on occasion, with the business revealing: "We don't use additives or sugars so she has been eating a really clean diet, with tonnes of fruit and vegetables, lean protein and complex carbs.
"Losing weight is actually relatively easy, you just control the calories. But glowing and being a happier person, that's all about eating a balanced diet, eating regularly and maximising the nutrition you are receiving."
Adele revealed this week: "Actually, I like myself more than ever. I feel so comfortable in my own skin. I really like how I look, I like who I am, I like everyone that I surround myself with."
But with her trademark charm, Adele added that she will never stop wearing her beloved Spanx underwear, joking: "It's like pumping a sausage skin full of meat."
PETE GERACIMO'S TOUGH REGIME
Pete Geracimo's clients are put through a demanding circuit of exercises five time, plus tough Tabata interval training, painful "lactic-burning" workouts, leg-strengthening hill sprints and super-toning, fat-burning water-running. Exercises include:
• Push a weighted sled for 40 metres (five times).
• Eight log presses (five times).
• Ten double rope swings (five times).
• As many burpees as possible in 30-second blocks of explosive movement then ten seconds to relax.
• As many push-ups as possible in 30 seconds then ten seconds' rest.
• As many lunges as possible in 30 seconds then ten seconds to rest.
• As many kettlebell swings as possible in 30 seconds then ten seconds' rest.
• As many dumbbell squats as possible in 30 seconds then ten seconds to rest.
• Hill sprints. Sprint up a steep hill or stairs as fast as possible for ten to 15 seconds, then slowly jog or walk down. Repeat for between ten and 15 minutes.
• Water-running. Intersperse a length of "sprinting" with a slower recovery pace.