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Our Verdict
The Sirtfood Diet is a low-calorie diet that focuses on the consumption of foods with polyphenols, which are natural compounds found in plant foods. The two-phase diet touts rapid weight loss as its main benefit.
As a registered dietitian, I found the Sirtfood Diet—focused exclusively on weight loss—as not an easy or tasty plan to follow. Prioritizing what the plan calls “sirtfoods” like red wine, blueberries and olive oil is doable, but making these foods the main focus of your diet isn’t realistic, or necessarily the healthiest way to eat.
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Key Features
- The diet claims benefits including rapid weight loss while retaining muscle mass
- Focuses on foods rich in polyphenols such as green tea, dark chocolate and red wine
- Consists of two phases that last three weeks
In 2017, Aidan Goggins and Glen Matten published the The Sirtfood Diet and The Sirtfood Diet Recipe Book after researching the eating patterns of those living in Blue Zones—several areas around the world where populations consistently live to be over 100 years old. They observed that these populations consumed high amounts of polyphenols, which are natural compounds found in plant foods.
The founders did an initial pilot test in which they claimed participants lost seven pounds in seven days, and since the diet’s initial publication, the eating plan has exploded in popularity for its alleged rapid weight loss benefits.
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The Sirtfood Diet at a Glance
- This diet has two phases, which include green juices and foods rich in polyphenols (or sirtfoods).
- A lot of time is needed for meal planning, food shopping and preparing meals.
- A very low calorie diet can promote weight loss, but not in a safe way.
How Does the Sirtfood Diet Work?
The Sirtfood Diet is based on the hypothesis that eating certain foods—specifically, certain types of polyphenols—can activate sirtuin, which are proteins that some research has linked to inflammation regulation and fat burning potential[1]. Triggering sirtuin mimics the effects of exercise and fasting, which can ultimately lead to weight loss, according to the plan. Allowable foods on this plan include foods rich in polyphenols, such as strawberries, red onions, turmeric, green tea, dark chocolate, apples, blueberries, capers and red wine. The diet also promotes consuming at least two servings of fatty fish, like salmon or tuna, weekly.
The diet is divided into two phases: phase one, which lasts seven days, and phase two, which lasts 14 days. The first part of phase one lasts for days one through three. During these three days, total calories are 1,000 per day, and a day’s worth of meals includes three homemade green juices and one meal rich in sirtfoods. The green juice recipe can be found on the diet’s website, and consists of kale, arugula, parsley, celery, green apple, fresh ginger, lemon and matcha powder. On days four through seven, calories are increased to 1,500 per day, where the dieter drinks two green juices and eats two meals rich in sirtfoods.
During phase two, a day’s worth of meals encompasses one green juice, three sirtfood meals and optional snacks like dates or walnuts. There are no calorie restrictions during this phase, with a focus on weight loss maintenance. Phase two lasts for 14 days.
Once both phases are complete, it’s recommended to continue adding sirtfoods to your menu and drinking a prepared green juice. How you continue adding sirtfoods is not explained clearly in the book, although there is a list of sirtfoods like artichokes, asparagus, popcorn, fava beans and many more that the authors encourage dieters to eat after they have completed the two phases.
The diet encourages repeating the two phases until weight loss goals are met, but recommends waiting at least a month before repeating phase one. In addition, the phases should not be repeated more than once every three months. You can repeat one or all the days of phase two as often as you would like, according to the book.
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How Much Does the Sirtfood Diet Cost?
The initial cost of this diet includes the book, The Sirtfood Diet by Aidan Goggins and Glen Matten, which is sold online for less than $30 (prices vary depending on the vendor).
The diet’s official website is free. Other costs include the food that needs to be purchased for meals and green juices, some of which can be pricey, such as lovage and matcha. Also, the green juice requires a juicer, and measuring cups are needed for all recipes. A scale is very helpful as well (all weight measures are given in cups, but also in grams if you want to be exact).
The Fine Print
As a registered dietitian and food safety consultant, I do not recommend this diet for those with a history of eating disorders. Additionally, I believe that this diet is not appropriate for individuals with diabetes, as very low calorie diets can affect the balance of blood sugar. Lastly, an athlete or someone who exercises heavily shouldn’t follow this plan, as it does not provide the calories or fuel needed to sustain exercise.
What Experts Say
According to Pittsburgh-based Leslie Bonci, a registered dietitian nutritionist and owner of Active Eating Advice, “the Sirtfood Diet changes the emphasis from macros to phytos (plant nutrients) but at the end of the day, you lose weight because your calories are lower.” Bonci also points out that in phase one, a seven pound weight loss in seven days will result in some muscle mass loss and, “going from calorie restriction in phase one to permission in phase two without direction and guidance is not the path to sustainability.”
The rapid weight loss this diet claims is also a red flag for Keith Ayoob, a registered dietitian nutritionist, associate professor emeritus of pediatrics at the Albert Einstein College of Medicine in New York City and owner of CutToTheChaseNutrition.com.
“You may lose the weight, but it won’t all be fat weight,” he says. “Weight lost on this diet is the old-fashioned way—because you’ve eaten fewer calories than your body spends. Great if you’re doing it with balanced meals and healthy foods…but that’s not a miracle, it’s what happens.”
With regards to the science, experts agree that there is insufficient evidence to back up the sirtfood claims. “The foods recommended on this diet are terrific and they’d be great in any healthful, balanced diet, but the claims made about sirtfoods helping you lose weight are way ahead of the science at this point,” adds Ayoob.
Long Beach, California dietitian Amanda Sauceda, owner of The Mindful Gut, LLC, does say, though, that this diet emphasizes healthy anti-inflammatory foods that are full of nutrients being researched for their brain, heart health and anti-cancer benefits.
“What is fascinating is that some of these foods may influence our genes—but I wouldn’t take it as far as saying they activate a ‘skinny” gene,’” she says. “At the end of the day, sirtfood foods are just another way to dress up a fad diet.”
The Sirtfood Diet Experience
I am a registered dietitian and wanted to see what would happen and how I would feel following this much-hyped diet. After reading over 250 diet books in my 20 plus years of practice, I really didn’t expect much going into it, and with all the rules in the book, I wasn’t expecting it was something I could follow long term—and I was right. I set out to try it for two weeks, and did increase the recommended sirtfoods, but I just could not tolerate those green juices.
The green juice that is taken throughout the diet needs to be prepared daily—for this reason, I recommend purchasing the ingredients in advance in bulk so you can have them on hand. The flavor of the juice is not very tasty, in my opinion, nor is the juice very satisfying (it left me hungry). As a result, I consumed other foods during the day, deviating away from the diet plan to satiate my hunger.
When it came to the actual sirtfood meals, I tried a few recipes from its website including the miso-marinated baked cod with stir fried greens and sesame, which was a tasty meal. However, the 7-ounces of cod was too much cod for me—I don’t like so much protein in one meal (5-ounces is usually my limit on fish), and I don’t love buckwheat. Some of the ingredients I was lucky to have at home, but they can be pricey or tough to find, like the buckwheat, mirin and tamari.
The eating plan also lacks fruit and fiber, which wasn’t great for my digestion. I didn’t try many other recipes, but did include more sirtfoods into my diet throughout the weeks as many are easily found at the grocery store.
Overall, I don’t recommend this plan. I really do not like having green juices that are not tasty for several meals—I want real food. The very restrictive nature of the first week is a turn-off for me as a person, and as a registered dietitian. Plus, in my expert opinion, the science doesn’t back up this plan to warrant such severe calorie restriction and unsatisfying green juices.
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