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The sirtfood diet has been around for a while now, but it was recently made famous again as one star reportedly followed the plan to lose a substantial amount of weight over the last few years.
Credited by many as being the diet behind Adele's weight loss (opens in new tab), the sirtfood diet involves eating specific foods that stimulate particular proteins in the body. "It's perhaps slightly less well known than the ketogenic diet (opens in new tab)," explains clinical nutrionist Suzie Sawyer but it's "high in polyphenols which are rich in antioxidants and highly protective of overall health."
The downside of the diet, she says, is that the sirtfood diet is "super-low in calories, starting around 1,000 a day initially, rising to 1500 calories per day after the first three days."
There's also not much evidence to say it's a diet that works any better than any of the other calorie restricted diets out there. And while no one should feel pressured into losing weight, if you're curious to try the sirtfood diet, this is everything that you need to know according to the experts.
What is the sirtfood diet?
The sirtfood diet is a strict, calorie-controlled eating plan that promises to reduce bodily inflammation, increase your life span and turn on the so-called "skinny gene".
The diet came into existence in 2015 after a study on proteins (opens in new tab), known as sirtuins, suggested that they regulate a whole host of functions in the body - including those to do with the metabolism, inflammation and lifespan.
It was thought that certain compounds in plants can increase the level of these proteins in the body and the foods containing these compounds were named "sirtfoods".
The book by nutritionists Aidan Goggins and Glen Matten is the leading guide on the sirtfood diet.
While it lay on the sidelines of the diet industry for a few years, following the revelation of Adele's weight loss early last year, the sirtfood diet has had a renewed interest.
Although the singer hasn't come forward to confirm that's how she lost her weight, many have suggested that the eating plan she stuck to was certainly similar to the sirtfood diet.
How does the sirtfood diet work?
The sirtfood diet works by encouraging people to eat certain foods (called sirtfoods), which stimulate the production of proteins called sirtuins. These are proteins in the body that have a specific effect on the body's metabolism. When combined with calorie restriction and exercise, the diet may trigger the body to produce more sirtuins.
"There are seven sirt proteins and each has a specific metabolic function," says Dr Deborah Lee of Dr Fox Pharmacy (opens in new tab). One of them, known as S1, "is associated with fat breakdown and weight loss".
This is the one that the sirtfood diet focuses on and this, our expert explains, "is why you may have heard of the sirtfood diet as the diet which activates the 'skinny gene' pathways in the body."
The S1 pathway is the same one commonly activated by fasting and exercise. It helps the body to burn fat, increase muscle mass and improve overall health.
But it's not only weight loss that the diet focuses on, explains Dr Lee. "The authors of the sirtfood diet believe that eating sirtfoods not only activates sirt genes but also helps to stabilise blood sugars and fight inflammation," she says.
"Sirtuins have been identified as having an important role in anti-aging too. Some scientists believe that increasing the dietary intake of sirtuins and doing more physical exercise may extend the human lifespan."
How much weight can you lose on the sirtfood diet?
Authors of the sirtfood diet claim that it can help you lose 7 pounds (3.2kg) in 7 days.
This is because your calorie limit is reduced to just 1000 calories per day during the first seven days. This total is made up of three green juices and one meal, chosen freely.
While there are certainly benefits to the sirtfood diet, it's arguable that the majority of the weight loss comes from this intense calorie restriction and combined exercise regime - rather than due to any real intervention from the sirtfoods.
For instance, many studies - including one from the American Journal of Clinical Nutrition (opens in new tab) - show that calorie restrictive diets are one of the most successful ways to lose weight. When you restrict the number of calories you eat to below your maintenance level, which is the number of calories your body needs per day to sustain typical function, you enter a deficit. The larger the deficit, the more weight you are going to lose as instead of taking its energy from food sources, you body takes its energy from other reserves - like water and fat.
Looking at how many calories in a pound of fat, the leading research on the subject (opens in new tab) concludes that a deficit of 500 calories per day will lead to 1 pound of weight loss. By eating just 1000 calories per day on the sirtfood diet, the average woman is in a deficit of double that so will naturally lose weight very quickly.
What do you eat on the Sirtfood Diet?
While the sirtfood diet may be low in calories, there are still lots of foods to choose from.
Top Sirtfood Diet foods
- Olive oil
- Red and White wine
- Matcha green tea
- Dark chocolate (85% cocoa)
- Birds-eye chillies
- Green Tea
- Medjool dates
"Sirtfoods comprise of a range of specific sirt-rich foods," says Dr Deborah Lee. "Examples include resveratrol, often found in grapes and red wine. Quercetin, found in buckwheat, onions and green vegetables. And omega-3 fatty acids, typically found in oily fish, nuts and seeds."
But the authors of the sirtfood diet insist that processed foods and those high in sugar should be avoided. And as Dr Lee says, while medjool dates are sirtfoods, "all dried fruits are high in sugar so don't overdo it."
"On the sirtfood diet, high-carb foods such as pasta, potatoes, beans and legumes are to be avoided as they are not sirtfoods. When following the diet, you should fill up on green vegetables instead."
But there's still some 'fun' foods left to enjoy. "Dairy foods such as milk, eggs and butter are permitted," Dr Lee says, but she warns about sticking to the quantities recommended in the recipes so you don't go overboard.
The biggest positive of the diet, which puts it in real contrast to other restrictive eating plans, is the green light on red wine, dark chocolate and coffee.
"These are actively encouraged on the sirtfood diet. You can drink two to three glasses of red wine per week, coffee and dark chocolate are all approved."
How to follow the Sirtfood Diet
The initial stage of the sirtfood diet involves juicing and fasting only. This may good for those who might want to shift a few pounds quickly but can be hard when it comes to preparation.
Dr Deborah Lee says:
- Organisation is key: "You will need to purchase the food ingredients for your first few days on the diet in advance."
- Make sure you have a proper juicer: "A blender or a NutriBullet won’t do – they just produce a green sludge."
- Choose your Sirtfood meals: "There are many recipes to choose from in The Sirtfood Diet book."
- Start at the right time for you: "Think ahead about what you have planned and how you can deal with this way of eating."
Yet, even with forward planning, the sirtfood diet can be difficult to start. "From a behavioural psychology point of view, it’s quite hard to implement all of its recommendations at once," says Alex Ruani (opens in new tab), UCL doctoral researcher and chief science educator at The Health Sciences Academy.
"It requires a lot of preparation, cooking skills, getting the right equipment (like a juicer instead of a blender), and making radical changes in the way we eat and when or how we eat. The sheer number of items to prepare may be off-putting even for someone who has excellent planning or cooking skills."
Plus, limiting the number of calories you eat every day will really be off-putting for some people. So, choose a time to start that doesn't clash with an event in your life that could derail your plan - like a holiday.
"The first week requires extreme caloric restriction, so it’s not an easy start for most people," says Alex.
Days one to three are most intensive. Your intake is just 1,000 calories – consisting of three juices and one meal.
Days four to seven are a little more lenient with a calorie maximum of 1,500 calories per day.
Creators of the sirtfood diet Aidan and Glen say that in order to combat the fasting period, people shouldn't focus on how much weight they are losing. Rather, they should look at the health impact on their body, how their clothes fit and whether their skin appears any better.
They also advise fasters to spread the juices out throughout the day rather than having them too close together. Consume the juices at least an hour or two before and after meals, they say.
You also need to be wary about exercising during the first stage when you are not consuming many calories.
"Although the diet promises losing fat while maintaining muscle mass, when you limit your calories severely, you will inevitably lose some muscle mass," says Alex. "And even more so if you exercise, as you’ll be more rapidly depleting glycogen stores in muscle, so the body starts breaking down muscle protein for fuel."
Is the Sirtfood Diet a long-term plan?
No, the sirtfood diet isn't suitable as a long-term healthy weight loss plan.
"The calorie restriction is severe. It may lead to symptoms such as headaches, feeling cold, constipation and difficulty sleeping," Dr Lee says. "Some people have also said that the diet may not contain adequate amounts of protein. Also, drinking copious amounts of fruit juice damages tooth enamel. It can be dangerous for your teeth."
If you're looking for better weight loss then you need to change your eating patterns forever, she says. "It's unlikely you could stick to the sirtfood diet indefinitely. A more rational approach would be just to add sirtfoods to your daily meals."
Can you eat meat on the Sirtfood Diet?
Yes, you can eat meat on the sirtfood diet.
The maximum amount allowed is 750g of red meat three times per week.
"Meat is a good source of leucine, an amino acid that enhances the action of S1,’ says Dr Lee. "But avoid processed meats such as bacon, salami, and ham as these are processed foods. Fish and poultry can be eaten as often as you like. Oily fish is recommended."
But eating meat is entirely optional. It's by no means an integral part of the plan. This means the sirtfood diet can be a vegetarian and vegan-friendly choice too.
Can you drink coffee on the Sirtfood Diet?
Yes, you can drink all fluids, including coffee, freely throughout all the stages of the sirtfood diet.
In fact coffee is a recommended part of the plan and is listed within the top 20 sirtfoods.
But if you do drink coffee, don't add too much milk. "Coffee should be black as milk can interfere with the absorption of some of the nutrients in the diet," Dr Lee says.
And as well as helping to produce more of those sirtuins, "drinking coffee can help you burn an extra 100 calories per day."
You may, however, wish to go easy on the caffeinated drinks when you're on the sirtfood diet. As well as evidence from 2016 that shows the overconsumption of caffeine can cause high blood pressure, there's the risk of insomnia and headaches (opens in new tab) - especially when combined with a low-calorie diet.
The Sirtfood Diet: a nutritionist’s verdict
Suzie Sawyers, clinical nutritionist at Alive!, (opens in new tab) says that, overall, there are some health benefits to the plan. But also some real gaps in the nutritional makeup of the sirtfood diet.
|✅ Encourages portion control ✅ May help people choose healthier foods ✅ Helpful as a short-term weight loss plan||❌ Low in B vitamins which are good for energy ❌ Low amounts of protein overall ❌ Bad side-effects due to low calorie intake ❌ Unsustainable due to low calorie intake|
"Certain foods are categorised as 'sirtfoods', including apples, blueberries, kale, dark chocolate, and green tea, turkey, chicken, and prawns. The diet is therefore low in energising B vitamins that whole foods such as beans and whole grains are rich in. Plus, total protein in the sirtfood diet is poor. For these reasons, and also the low-calorie intake, it is not a sustainable way to lose weight for most people," she says.
"Any diet plan where calorie intake is severely restrictive can only be followed for short periods. Especially since hunger pangs can be debilitating for many people. However, it may be good for a 'quick fix' with a view to following a more sustainable eating plan thereafter.
"And with all diets, whatever plan, you will be missing out on vital nutrients to fuel the body. So it is essential to take a multi-vitamin and multi-mineral supplement daily. I swear by the Alive! Multivitamin gummies. They are full of a-z of nutrients and they contain 26 fruit and vegetables, as well as a host of botanical blends to help with all wellness needs.”
While Dr Deborah Lee agrees that it's not a long-term solution for weight loss. But in the short-term, it may be a way to jumpstart your diet.
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"We all eat too much and have too large portion sizes. If this diet helps people choose healthy food, and eat little and often, this has to be a good thing," she says. "The diet is creative, with interesting recipes and offers a wide choice of foods."
Grace Walsh is a Features Writer for Goodto.com, covering breaking news health stories during the Covid-19 pandemic as well as lifestyle and entertainment topics. She has worked in media since graduating from the University of Warwick in 2019 with a degree in Classical Civilisation and a year spent abroad in Italy. It was here that Grace caught the bug for journalism, after becoming involved in the university’s student newspaper and radio station.
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