When Adele showed up on vacation in Anguilla at the beginning of January looking slimmer—a whole lot slimmer—and happy, frolicking in the surf and posing for pictures with her pals Harry Styles, James Cordon, and the local restaurant servers at the resort, everyone asked how she did it. How did she lose nearly 100 pounds? She reportedly told fans that she has lost "seven stone" (a stone is 14 pounds). Other news outlets say she lost 99  pounds, or 45 kg—all in a fairly short amount of time.

Adele @instagram

The Daily Mail in London reports that Adele accomplished most of the weight loss through green juices and keeping to only 1,000 calories a day. She also worked with a trainer, her "Brazilian Body Wizard" to help stay strong and toned through the transformation. But most accounts pin her dramatic weight loss on diet, one that relied on plant-based foods.

Goodhousekeeping reports that Adele used the Sirtfood diet, sending the world into a frenzy to find out what that is. Turns out it's a plant-based diet high in antioxidants which is supposed to rev metabolism and turn on the body's stress-fighting longevity genes. The founders call it the "Skinny Gene" diet but there is little science to back up the claims that Sirtfoods "mimic fasting and exercise." What they do in fact accomplish is they help your body be healthier. So that's something.

Adele's Weight Loss Motivation.

People Magazine just published a report that Adele wanted to transform herself to be a better mom to her 7-year-old son Angelo, whom she shares with her ex, Simon Konecki. The report has a source explaining: Adele's weight loss transformation was because the singer knew 'she had to change something:'

“It’s easy to just focus on her physical transformation, but this is really about something bigger,” the insider told People. “She got to the point where she didn’t feel great. She knew she had to change something because she wants to be the healthiest mom possible.”

“Her whole focus during the weight loss journey has really how been all about how she can be healthier and how can she treat her body better. “It was never about losing weight. Her weight loss happened because she has cut down drinking and is eating more real food. But she now loves her physical transformation too. She is more confident, dresses differently and she just seems happier overall.”

Harry Styles, Diet Coach or BFF?

So how did Adele do it? One answer, also reported in the press, is that her friend Harry Styles has been leading her on his favorite hikes in Malibu, and taking her to do HIIT workouts together (High-Intensity Interval Training). The other is that she has been following the Sirtfood diet. Yet another news story in the British press said that Styles and Adele's relationship has grown increasingly "flirty" so there's always that. Nothing like a little flirtation to rev up the metabolism.

What the Heck Are Sirtfoods?

But let's get back to the Sirtfood Diet. Anyone who has never heard of it before, it's called "the skinny gene" diet. But we prefer to think of it as the plant-food diet, with an emphasis on antioxidant-rich foods containing polyphenols (found in tea, wine, and chocolate). Polyphenols are naturally recurring agents in foods than, along with vitamin C and E and carotenoids, are known as antioxidants because they protect the body's cells against oxidation and pathogens such as cancer, inflammation, and heart disease. So, whether the Sirtfood diet will help you lose even one stone is up for debate, but they will help you live healthier, longer.

The Sirtfood diet has been around for several years. Designed by nutritionists Aidan Goggins and Glen Matten, and made more popular by trainer Pete Geracimo, who put his clients Adele and Pippa Middleton on it, the Sirtfood Diet proscribes eating foods that contain polyphenols to help the body burn fat. How this happens is a complex series of chemical and biological functions, but if a client increases their workout intensity and changes how they eat, these foods will help them lose more weight.

What Exactly Do You Eat on a Sirtfood Diet?

Some of the Sirtfoods on the diet are arugula, celery, coffee, red onion, extra virgin olive oil,  and dark chocolate. Top 20 Sirtfoods are vegetarian chilli (chilli powder has polyphenols), buckwheat, celery, cocoa, coffee, extra virgin olive oil, kale, lovage (a leafy herb) Medjool dates, parsley, red chicory, red onion, rocket (a bitter leaf) soy, strawberries, turmeric, walnuts. Most diets cut out alcohol (and some even banish caffeine) but this one allows not only coffee and matcha green tea but also red wine!

The diet creators looked at populations that are the healthiest, called "Blue Zones," and discovered that the slimmest people with the most longevity ate the most plant foods—some five times more than the typical Western diet.

The plant-rich diets also contained the most polyphenols. So Goggins and Matten went looking for the foods with the most polyphenols and came up with their list of the top 20 foods to eat on repeat. They claim these "mimic the effects of fasting and exercise through activating our sirtuin (aka ‘skinny’) genes" and the press picked up that claim, calling Sirt the "skinny gene" diet.

Is There Really a Skinny Gene?

When you look up the definition of "sirtuin," longevity is even more relevant, since sirtuin refers to any enzymes that are thought to regulate cellular aging and resistance to stress. So, whether the Sirtfood diet helps you lose weight, it will definitely help your anti-aging and anti-stress mechanisms. Maybe that's why Adele's skin is glowing and she looks so carefree on holiday!

Whether or not that is scientifically provable or even remotely possible, The Beet is all for eating more plant foods and adding more anti-oxidant based foods that are high in fiber to your diet. If we were to design a diet it would definitely include most of the items on this list (with red wine in moderation).

That said, we love the "Someone Like You" singer, who, at 31, has found her happy place—and seemingly her happy weight, too.