When it comes to trendy eating plans, the Sirtfood Diet has been relatively unknown… until recently. The diet is being widely cited as the catalyst behind singer Adele's reported near-50-pound weight loss—although the singer hasn't confirmed it herself.Still, her slimmed down look has had the Internet abuzz, and she even joked about it on a recent Saturday Night Live appearance in October, saying she was only able to bring "half" of herself to New York due to "COVID-19 travel restrictions."What is the Sirtfood Diet?The Sirtfood Diet is a three-week weight-loss plan centered around foods rich in polyphenols. They've been dubbed "sirtfoods" because animal studies have shown that polyphenols activate sirtuins, a group of seven proteins that might potentially promote healthy aging and prevent chronic disease, among other supposed benefits. (Related: 100 Unhealthiest Foods on the Planet.)Founders Aidan Goggins and Glen Matten created the diet in 2016 after noticing that the potential benefits of polyphenol-rich plants were being studied in the context of medicine, but not nutrition, and that some of the world's healthiest populations ate more plant foods.As a result, the pair identified the most polyphenol-rich foods and aimed to find out whether eating more of them would offer similar benefits.What Foods are Allowed?The Sirtfood Diet lists these as its "top 20" foods:bird's eye chilibuckwheatcaperscelerycocoacoffeeextra virgin olive oilgreen tea (especially matcha)kalelovageMedjool datesparsleyred chicoryred onionred winerocketsoystrawberriesturmericwalnutsWhat are the Limitations?These recommended foods—including chocolate, red wine, and coffee—are generally healthy in moderation. However, there still isn't enough research on polyphenol's effect on humans to back up the claim that sticking to these foods can "supercharge weight loss and stave off disease.""There's nothing magical about having these components from the food that's going to make you lose weight," Lisa Young, RDN, Ph.D., professor of nutrition at NYU and author of Finally Full, Finally Slim, tells Eat This, Not That!. "There's no research to prove that in humans, so that's more like wishful thinking."The other main aspect of the diet is calorie restriction, particularly in the first week. It prescribes just one sirtfood-rich meal, plus three glasses of sirtfood green juice, on each of the first three days. That's 1,000 calories or less each day.Young cautions against eating less than 1,200 calories per day and finds one solid meal per day to be too restrictive. "I don't think if you do it for a few days, it's dangerous per se, but it's certainly not a healthy way to lose weight," Young cautions, adding that the 7-pound weight loss in seven days that the diet guarantees would be mostly water weight.Days four through seven on the plan call for two green juices and two meals per day, restricting calories to 1,500. This, as well as the rest of the three-week plan (which calls for three balanced meals a day and the inclusion of sirtfood juice), is reasonable as far as Young can see.What's the final verdict?The Sirtfood Diet isn't necessarily unhealthy, except for the extreme calorie restriction and rapid weight loss during the first few days—both of which are not sustainable, Young says. The diet's biggest downfall, though, may be the benefits it advertises, which haven't been verified by research.In general, eating more nutritious foods like those the diet suggests isn't a bad idea. "Enjoy those foods—not because there's magic to them, but because they're healthy foods," Young says.For more weight loss news, make sure to sign up for our newsletter.Read the original article on Eat This, Not That!