The Sirtfood diet has been in the news again this week after singer Adele showed off her slimmed-down figure on the US comedy show Saturday Night Live.
Adele has previously credited her significant weight loss to the Sirtfood diet. Following her appearance on SNL, there was a spike in people searching the diet on Google.
But what exactly is the Sirtfood diet, and does it work?
What’s the premise?
Two nutritionists in the United Kingdom launched the Sirtfood diet in 2016.
The premise is that a group of proteins called sirtuins, which are involved in the regulation of metabolism, inflammation, and aging, can be accelerated by eating specific foods rich in a class of phytonutrients called polyphenols.
Phytonutrients are chemical compounds plants produce to help them grow well or defend themselves. Research is continuing to shed light on their potential benefits for human health.
Read more: Phytonutrients can boost your health. Here are four and where to find them (including in your next cup of coffee)
The idea is that eating foods rich in polyphenols, referred to as “Sirtfoods”, will increase the body’s ability to burn fat, boosting metabolism and leading to dramatic weight loss.
Common Sirtfoods include apples, soybean, kale, blueberries, strawberries, dark chocolate (85% cocoa), red wine, matcha green tea, onions, and olive oil. The Sirtfood diet gets some of its fame because red wine and chocolate are on the list.
Two phases
The diet involves two phases over three weeks. During the first three days, total energy intake is restricted to 4,200 kilojoules per day (or 1,000 Calories).
To achieve this, you drink three sort food green juice drinks that include kale, celery, rocket, parsley, matcha green tea, and lemon juice. You also eat one “Sirtfood” meal, such as a chicken and kale curry.
On days four to seven, you have 2 to 3 green juices and one or two meals up to a total energy intake of 6,300 kJ/day (1,500kcal).
During the next two weeks — phase two — total energy intake should be in the range of 6,300-7,500 kJ/day (1,500-1,800 kcal) with three meals, one green juice, and one or two Sirtfood snacks.
There’s a diet book available for purchase that gives you the recipes.
After three weeks, the recommendation is to eat a “balanced diet” rich in Sirtfoods, along with regular green juices.
Red wine is a ‘Sirtfood’. But it should still be enjoyed in moderation. Kelsey Knight/Unsplash
Positives
The idea of losing a lot of weight in just three weeks will appeal to many people.
The eating plan encourages a range of polyphenol-rich foods that are also good sources of vitamins, minerals, and dietary fiber and would be recommended in a range of diets designed to assist with weight management or as part of a healthy, balanced eating plan.
A weight loss diet will be effective if it achieves sustained total daily energy restriction. So the biggest benefit of the Sirtfood diet is the day-to-day energy restriction — you are likely to lose weight if you stick to it.
Also, the exclusion of energy-dense, ultra-processed “junk” foods will help lower the risk for chronic disease.
But there are drawbacks to consider, too.
Negatives
Watch the portion size for some of the foods listed, such as red wine and chocolate.
Like most restrictive diets, phase one may be challenging and is not recommended for people with underlying health conditions without the supervision of a health professional.
Read more: Health Check: what’s the best diet for weight loss?
The rapid weight loss in the first phase will reflect a loss of water and glycogen, the stored form of energy in muscles and the liver, rather than being all body fat.
Rapid weight loss can increase the risk of gallstones and amenorrhoea (missing menstrual periods).
The food list includes specific products that may be hard to locate in Australia, such as lovage, a European leafy green plant whose leaves can be used as an herb, roots as a vegetable, and seeds as a spice. Some other items on the list can be expensive.
The Sirtfood diet can result in rapid weight loss, but that’s not always a good thing. Shutterstock
Sirt science
Most research has looked at the sirtuin-mediated effects of energy restriction in worms, mice, or specific body tissues. No studies have tested the effect of diets that vary polyphenol content on the action of sirtuins in mediating weight loss.
A search on PubMed, the scientific database of research studies, didn’t locate any human trials of the Sirtfood diet. The short answer about whether the Sirtfood diet works or not is we don’t know.
The authors’ claims about effectiveness are based on anecdotal information from their research and from personal testimonials, such as the one from Adele.
