Shaun Ward MSc ANutr
One of latest diet crazes that everyone is talking about is the sirtfood diet, which is a diet rich in ‘sirtfoods’.
According to creators of this diet, sirtfoods are special because they can activate specific proteins in the body called sirtuins.
By doing so, combined with eating fewer calories, the creators claim that it will inevitably lead to rapid weight loss, all while maintaining muscle mass and protecting against chronic diseases.
What Are Sirtuins?
Sirtuins are a class of enzymes in the body that influence aging by regulate a variety of functions, including metabolism, inflammation and longevity. These enzymes are activated when the body is low in energy, such as during a calorie deficit (eating less than one burns in a day).
That is why sirtuins are said to “mediate” the effects of caloric restriction.
Sirtuins are found mainly in the nucleus of cells, but also in the mitochondria and the cytoplasm.
As mentioned, sirtuin activity depends on the energy state of human cells, as they are only activated by the presence of NAD (a coenzyme which signals that the body is low on fuel).
There is ample evidence that when sirtuins are activated they not only alter changes in energy metabolism, but also improve responses to cell damage, insulin sensitivity, inflammation, and hormonal systems.
This makes sirtuins an excellent link between the nutritional status of the human body and the cellular responses which react to these nutritional states.
In other words, during caloric restriction, sirtuins are activated by energy regulators within our cells, and then sirtuins signals for changes at a genetic level to influence metabolic functioning and health.
For example, there may be an upregulation in the genes involved in insulin signaling, cancer prevention, fat oxidation, DNA repair, and even mood.
There are 7 different types of sirtuins which are all responsible for different roles within the body. Some examples are:
- SIRT1 can activate pathways involved with cancer protection by inhibiting tumor growth in the gut and pancreas   . SIRT1 can also reduce the transcription of pro-inflammatory genes .
- SIRT3 regulates mitochondrial function and fat oxidation  . It can also damage from free radicals by improving antioxidant defense systems .
- SIRT6 suppresses the role of key activators for inflammation such as NF-κB.
The roles of the remaining 4 sirtuins are less researched but are still speculated to promote good health.
Role of The Sirtfood Diet?
The sirtfood diet looks to go 1 step further than calorie restriction to activate sirtuins.
It does so by revolving the diet around the consumption of supposedly “sirtuin-activating” foods, combined with caloric restriction.
The list of the “top 20 sirtfoods” provided by the Sirtfood Diet include:
- Red wine
- Extra virgin olive oil
- Dark chocolate (85% cocoa)
- Matcha green tea
- Arugula (rocket)
- Bird’s eye chili
- Medjool dates
- Red chicory
The sirtfood diet also strongly encourages the frequent use of the sirtfood green juice which includes:
- 75 grams of kale
- 30 grams arugula
- 5 grams of parsley
- 2 celery sticks
- 1cm of ginger
- Half a green apple
- Half a lemon
- Half a teaspoon of green tea
Based on these foods, the sirtfood diet is split into 2 distinct phases:
- Phase 1: This lasts for 7 days and involves severely restricting energy intake to just 1000 calories a day. This includes 3 green juices and 1 sirtfood meal a day (from the sirtfood recipe book). This is intended to accelerate weight loss and is claimed to lose 7 pounds in 1 week. Optionally, on days 4-7 of this week, calories can be increased to 1500 per day by replacing 1 green juice with an additional sirtfood-rich meal from the book.
- Phase 2: This lasts for 2 weeks and is more of a maintenance phase where weight loss still occurs but to a lesser extent. There is no set calorie intake for this phase, but all meals should be sirtfood-meals in the recipe book, and it is still required to drink 1 green juice a day.
Does The Sirtfood Diet Work?
Anyone who follows the sirtfood diet will notice a considerable amount of weight loss within phase 1 and 2. This is due to the extremely low caloric intake that is similar to that seen in most fad diets.
However, outside of the large calorie restriction there is no convincing evidence to suggest the sirtfood diet is more better for weight loss or health than any other calorie-restricted diet.
The only real study that supports the diet was conducted by its creators, where they found that participants on the diet lost 7 pounds in 1 week whilst maintaining or even gaining muscle mass.
However, this study is only found on their website and has never been analyzed by a scientific panel or been deemed a reliable source of information.
The result of the study is also not surprising, as any diet that restricts calories to 1,000 per day will see the exact same results – whether sirtfoods are included or not. This is because during a sudden period of energy deprivation, the body will burn through its carbohydrate stores in the muscle tissue and liver, as well as losing a considerable amount of water weight (that is usually stored alongside the carbohydrates in muscle). In fact, in all studies that have 1 week of extreme calorie restriction, only about ~30% of the weight seems to comes from fat, with the majority coming from water, muscle and carbohydrate stores .
Not to mention that this type of eating plan is simply not sustainable in the long-term.
Firstly, eating such a limited amount of food (even if they are “healthy” foods) cannot meet all of the body’s nutritional needs. It will undoubtedly cause micronutrient deficiencies and lead to side effects and safety issues if an individual sticks to the diet for long enough. Fatigue and irritability are going to be hard to avoid in phase 1.
Secondly, when normal eating habits are restored after this diet is finished, it is likely the lost weight will quickly return. Current evidence demonstrates that 30-35% of lost weight is regained one year after following a diet and 50% of people return to their previous weight by year 5 after weight loss . This is due to a reduction in ones metabolic rate after extended periods of severe caloric restriction , coupled with an elevation in hunger hormones such as leptin that tend to lead to binge-eating after a diet .
Does Eating Sirtfoods Help?
There is a small amount of evidence that certain foods are be able to increase the activity of sirtuins outside of weight loss and caloric restriction.
For example, a polyphenol called quercetin found in onions can slightly increase Sirt1 .
However, this type of evidence is extremely scarce, and to base an entire diet on sirtfoods is completely illogical.
There is also no evidence to suggest sirtfoods have any unique effect on weight loss – which is the main aim of the sirtfood diet.
What about Red Wine And Dark Chocolate?
A major selling point of the sirtfood diet is that people are allowed to eat dark chocolate and red wine as these are supposedly able to activate sirtuins.
Now, it is important to point out that there is nothing wrong with eating these foods as part of a balanced diet. Red wine and dark chocolate in small amounts may positively affect health , inflammation  , and lower the risk of heart disease .
However, no diet should encourage the consumption of these foods due to the obvious dangers associated with their consumption in excess.
This is especially important when talking about a diet that has only 1000-1500 calories a day, as eating calorie-dense foods such as these will end up taking up a large chunk of one’s daily calorie allowance.
The sirtfood diet is one that is rich in foods that can supposedly increase the activity of sirtuins in the body.
Sirtuins are enzymes in the body that are activated by caloric restriction and are partly responsible for the health benefits of reducing calorie intake.
However, there is no evidence to suggest that certain foods can significantly increase the activity of sirtuins outside of caloric restriction.
The severely restricted calorie allowance of the sirtfood diet also makes the diet unsustainable and raises concerns for nutritional deficiencies.