As Americans continue to grapple with their weight, the diet industry has surged to more than $20 billion annually. Some of that money comes in the form of the roughly 5 million diet books that are sold in the United States each year, according to data from Nielsen BookScan.
In 2017, yet another diet book hit the shelves promising to solve the problem many people have with obesity. “The Sirtfood Diet” was written by Aidan Goggins and Glen Matten, who both hold master’s degrees in nutritional medicine and are based in the UK. They refer to themselves as “nutritional medicine and pharmacy experts,” and the book promises diligent readers the keys to eating more while weighing less.
The sirtfood diet claims to help dieters lose 7 pounds in seven days, while offering a range of health benefits including:
“The sirtfood diet gets its name from a group of proteins called sirtuins,” says Kimberly Pierpont, a registered dietitian with the Ohio State University Wexner Medical Center. Sirtuins are a type of polyphenol found in plant foods, and they “work at a cellular level in the human body to promote cell homeostasis and longevity.”
Sirtuins are also involved in the metabolic process, and the sirtfood diet capitalizes on this connection. “The sirtfood diet focuses on foods high in polyphenols with claims they will ‘trigger the sirtuin pathways that impact metabolism, aging and mood,'” Pierpont explains. The idea is that consuming food high in these polyphenols can help you activate the sirtuin (or ‘skinny’) genes that mimic the effects of fasting and exercise.
“When celebrity nutritionists from the United Kingdom created this diet, it was hypothesized that these natural plant compounds along with calorie restriction may be able to increase the level of sirtuins in the human body, therefore producing benefits such as weight loss that can lead to protecting you from chronic diseases,” says Reema Kanda, a registered dietitian nutritionist with the Hoag Orthopedic Institute in Irvine, California.
What Are Sirtfoods?
The sirtfood diet focuses on consuming foods high in sirtuin. These so-called sirtfoods include:
Other foods that contain sirtuins at lower levels than the 20 above but still appear on the sirtfood diet include:
“All of these foods have literature supporting their health benefits in chronic disease prevention,” Kanda says, so in terms of foods that are included, they aren’t bad for you. The diet outlines that meat and animal products can be consumed while on the plan, and many recipes include chicken, shrimp, salmon and other lean meats. Eggs are permitted and dairy is limited, but feta cheese and semi-skimmed milk appear in some recipes.
How the Sirtfood Diet Works
The sirtfood diet process is broken into two phases.
The first phase lasts seven days, and during this time, the plan is prescriptive:
- Days 1 through 3: You’ll have three sirtfood green juices (recipe below) plus one sirtfood-rich meal for a total of 1,000 calories per day.
- Days 4 through 7: You’ll have two sirtfood green juices, plus two sirtfood-rich meals, which increases calorie intake to 1,500 calories per day.
Kanda says the first phase “may be challenging for someone who is highly active and requires additional calories.”
The second phase lasts 14 days in total (days 8 through 21), and during this time, you’ll consume one sirtfood green juice, plus three sirtfood-rich meals. No calorie recommendation is given. “The sirtfood diet recommends repeating the two phases as needed,” until you hit your weight goal, Pierpont explains.
“After the three-week diet is over, no guidance is provided on foods to avoid, but dieters are encouraged to incorporate high sirtfoods into your daily meals,” Kanda says.
Sirtfood Green Juice Recipe
You can make the sirtfood green juice at home with the following recipe:
- 75 grams kale.
- 30 grams rocket (aka arugula).
- 5 grams parsley.
- 2 celery sticks.
- 1/2 green apple.
- 1-centimeter piece of fresh ginger root.
- Juice of half a lemon.
- 1/2 teaspoon matcha green tea.
Juice ingredients in a juicer, not a blender. You can hand-squeeze the lemon and mix the matcha green tea directly into the juice. Matcha green tea contains caffeine and is only recommended to be added to your first one or two green juices of the day.
The diet “appears easy to follow since recipes are provided,” Kanda says. “After the three weeks, dieters are recommended to begin including foods high in sirtuins as much as possible into meals without providing specific guidelines. You can also repeat the two phases as much as you wish.”
The sirtfood diet’s primary aim is rapid weight loss. As such, it “can be beneficial to anyone who wants to try a new diet to jump-start their weight loss journey or begin making healthier food choices,” Kanda says.
However, she cautions that if you have a “serious health condition that requires a high protein diet or a low carbohydrate diet,” this might not be a good choice for you, as the diet may provide less protein than you need, especially during the stricter first phase. Plus, because the diet is intended as a short-term fix, “it wouldn’t really promote long-term health benefits.”
Nevertheless, “the foods allowed on this diet can be incorporated into a long-term nutrition and lifestyle program while incorporating food from all food groups that can promote many health benefits and prevention of chronic diseases,” Kanda says. You can create a healthy eating plan that includes many of the foods championed by the sirtfood diet, without having to be super restricted.
While the sirtfood diet can help you shed weight quickly, which could lead to health improvements, it can also “be dangerous due to the calorie restriction in phase 1,” Pierpont says. Consuming only 1,000 calories per day in days one through three and 1,500 during days four through seven is significantly less than the 2,000 calories per day the average adult is typically told to consume.
“Most diet plans utilize a calorie deficit to achieve weight loss,” Pierpont says, “but these calorie goals are never one-size-fits-all. Individual calorie needs should be determined using an evidenced-based calculation or indirect calorimetry,” a type of test that uncovers how many calories your body needs to meet all basic functions.
When determining your individual caloric needs, you need to consider your:
- Activity level.
“Essentially, a 1,000 or 1,500 calorie per day diet may not be realistic or sustainable for all people,” Pierpont says.
In addition to calorie restriction, the diet also relies heavily on the sirtfood green juice concoction. “Juicing fruits and vegetables leaves behind most, if not all, fiber,” Pierpont says, and fiber is an important element of a healthy diet that may help with weight loss.
“The typical American already struggles to get the recommended 25 to 35 grams of fiber daily,” Pierpont says. Fruits and vegetables are high in fiber, so consuming fresh, whole fruits and vegetables is good for boosting fiber intake, but juicing them removes that fiber. “Juice also tends to be high in carbohydrates and should be consumed sparingly by people with diabetes or anyone struggling to control blood sugar levels.”
Kanda notes that “people with diabetes should use caution, as the first week is very limiting in fiber and protein. Even though the recommended three green juices per day contain healthy ingredients, they lack fiber, and the sugar content in juices can promote high blood glucose in people with diabetes.”
Pierpont also notes that the diet focuses heavily on 20 primary sirtfoods, (the first 20 items on the list above) but this limits variety. The concern with that limit to variety is that it could set you up for a vitamin or mineral deficiency if followed long term. “There’s also only one recipe for green juice, which could become repetitive,” she says, as you’ll be drinking a lot of this beverage, especially in the first phase of the plan.
Does It Work?
Despite these concerns, the sirtfood diet is hot right now, aided by celebrity endorsements from the singer Adele, MMA fighter Conor McGregor and boxer David Haye, who have all used it for weight loss. The plan markets itself as a way of losing 7 pounds in seven days, and Adele reportedly dropped more than 100 pounds following this protocol. But her result is not typical, and for most ordinary folks, the restrictive nature of the diet will make it a short-lived experience that may not result in sustainable weight loss.
“I believe you can lose weight on the sirtfood diet due to the calorie deficit and the adoption of a plant-based diet – all the sirtfoods listed are plants,” Pierpont says. “But I don’t believe this diet is the most effective or personalized way to lose weight.”
Kanda also says that “this diet will not work long term.” The 21-day period is “too short to produce long-term health benefits and long-term successful weight loss.” The restrictive nature of the diet is not conducive to staying on it long-term. As such, many folks may try it, lose some weight, get bored and then rebound with their weight.
The International Food Information Council Foundation agrees that the sirtfood diet is “not science-based or sustainable,” noting that the restrictive nature of the diet is problematic, and for some, that could trigger eating disorders.
Scientific evidence supporting the diet is virtually nonexistent. While there has been some research into the potential benefits of sirtuins, nearly all of which has been conducted in animals or cells in a lab rather than in people, no studies have yet looked at the sirtfood diet specifically and most importantly how it might impact health and wellness over the long term. The IFICF instead promotes mindful, intuitive eating following guidelines for healthy food choices that look more like the Mediterranean diet.
“Many of the foods recommended on this diet have healthful properties, however there are no long-term human studies to determine if eating foods high in sirtuins is truly the reason for one’s successful weight loss or longevity. In addition, restricting calories may produce unpleasant symptoms like fatigue and headache,” Kanda says.
If you follow the sirtfood diet faithfully for the 21-day, two-phase program, you’ll likely lose some weight as you would on any other calorie-restricted diet. It’s also likely that those losses will be mostly water weight rather than fat loss, which means the weight is very likely to return when you shift back to a less restrictive and more normal eating pattern.
However, the 20 foods high in sirtuins that the diet promotes are “all healthy foods we should incorporate into our diets,” Pierpont says. “And the recipes on their website offer creative and delicious ways to prepare these foods.” Many recipes are freely available on the website, and you can find the book in your local library. That said, she adds, “I do think we should include more than just these foods in our diet for variety.”