The Sirtfood Diet is having (another) moment. After Adele recently hosted Saturday Night Live, a barrage of tabloid news articles pummeled the internet explaining that her recent weight loss was due to her change-up in diet.
Adele joins Pippa Middleton and–on the complete opposite end of the spectrum–Conor McGregor as supposed fans of the Sirtfood Diet eating plan.
The Sirtfood Diet promises that you can lose up to 7 pounds in 7 days, which is a heck of a thing given that most credentialed weight loss experts recommend that 1 to 2 pounds of weight loss a week is healthy.
Not only is how much weight you lose on the Sirtfood Diet controversial, but so is the way that you’re encouraged to lose that weight. Plus, even though the diet was created by two guys with a background in nutrition, critics say that their approach to sustained weight loss is flawed, at best, and dangerous, at worst.
The Sirtfood Diet is highly restrictive, say critics, to the point of being untenable, and no serious scientific research has backed up its claims. Like any trendy diet, you should approach it–and the celebrities trumpeting its benefits–with caution.
Still, if it’s working for celebrities (and royalty!), then surely there’s proof that it does work for some people, right?
Before you undertake the dramatic shift in eating that is the Sirtfood Diet, it’s time to inform yourself of what the plan entails.
Here’s everything you need to know about the Sirtfood Diet.
What is the Sirtfood Diet?
Founded by U.K. nutrition experts, Aidan Goggins and Glen Matten, the Sirtfood Diet promises to stimulate the “skinny gene,” or the proteins under the SIRT1 gene, to counteract the effects of inflammation and weight gain, as well as aging.
The Sirtfood Diet is based on the principle that certain foods activate sirtuin, a (highly controversial) protein in the body that is alleged to help regulate metabolism and offer cell protection to slow down the aging process.
Proponents of the diet say that eating sirtuin-rich foods like green tea, kale, blueberries, salmon, and citrus fruits can give your body a steady metabolic boost. This boost allows you to lose weight fast. Such foods are also packed with polyphenols, which are antioxidants that better your skin and heart, says Brooke Alpert, R.D. and author of The Diet Detox.
What do you eat on the Sirtfood Diet?
The Sirtfood Diet is split into two phases.
The first phase, which lasts three days, requires you to restrict your calorie intake to 1,000 calories daily. You do this mainly by drinking three green juices and one sirtfood-rich meal per day. (You increase your meal count from days 4 to 7 to two meals and two green juices per day.) The second phase, the “maintenance” phase, lasts 14 days and requires you to eat three sirtuin-rich meals and one green juice per day.
Sounds … delicious?
Does the Sirtfood Diet work?
While the promise of the Sirtfood diet is intriguing, and while restricting your calories might in fact lead you to lose weight in the short-term, the diet is flawed.
First things first: the Sirtfood Diet is very restrictive and focuses heavily on counting calories. It also requires you to cut out some major food groups and downsize portions to an extreme, if only temporarily.
So for the first week or so, you might be missing out on lean proteins (beef, poultry, and legumes), which are key for building and maintaining muscle. While you’re still allowed to eat olive oil and walnut (both of which are sources of sirtuin), the total daily calorie count for the first week is extremely low–less than 50 percent of what the average active guy needs. The Sirtfood diet may also create deficiencies in essential nutrients, like calcium and iron.
Plus–and here’s the big thing–it’s also unclear whether sirtuin can actually cause weight loss to begin with.
To date, there have been no human studies definitively linking sirtuin-rich foods to weight loss. It’s more likely that drinking juices that are high in greens and low in sugar for most of the day can easily cause short-term weight loss on its own. If you’re getting fewer calories and staying hydrated, it makes sense that you’ll shed a few pounds.
Kristen Smith, M.S., R.D., a spokesperson for the Academy of Nutrition and Dietetics, backs this up. “It is difficult to decipher whether the rapid weight loss promised in the first week of the diet is attributed to the significantly low-calorie diet recommended or related to the fat-burning powers of sirtuin-boosting foods,” she says.
Basically, “regardless of the sirtuin-boosting foods, people are going to lose weight on a 1,000-calorie diet,” she says.
Alpert agrees. “The authors say that people can lose up to 7 pounds in 7 days but I wonder how much of this weight actually stays off for longer than one month, if that long,” she says.
Even if you lose weight during that first week, it could be primarily water weight, which means you might gain it back once you start taking in more calories. In fact, you might even gain more weight: as Men’s Health has previously reported, when you lose a lot of weight quickly, your body’s metabolism actually slows down, because your body is trying to make up for its reduced calorie intake.
Are there any side effects to the Sirtfood Diet?
While it likely won’t do much damage for you to eat so little in the short-term, if you’re not used to eating so little during the day, it can cause fatigue, nausea, impaired mental focus, and headaches, says Smith.
This diet may also lead to some, um, unpleasant bowel movements if you’re not getting enough fiber. What’s more, you might get bad breath, which can be a side effect of not eating enough.
The Bottom Line
While the Sirtfood Diet is likely to lead to short-term weight loss, it is ultimately so restrictive that it’s not sustainable. And if you’ve ever had an eating disorder or a complicated relationship with eating in the past, it’s best to avoid it altogether, says Alpert.
“I wouldn’t recommend such a low calorie intake for anyone. Extreme dieting sets people up for terrible eating habits and overeating when it’s over,” she says.
That said, there’s nothing wrong with eating more fish, berries, and leafy greens, and having a green juice that’s low in sugar could be a great addition to an already balanced diet.