Is the Sirtfood diet the secret to Adele's dramatic weight loss?

Annie Hayes
·6-min read
Photo credit: Steve Granitz - Getty Images
Photo credit: Steve Granitz - Getty Images

From Netdoctor

The Sirtfood diet generated a huge buzz recently after news reports linked Adele's dramatic weight loss to the nutrition programme, which famously includes red wine and chocolate. Along with personal training and Pilates, it's thought to be the secret to the singer-songwriter's gradual seven-stone transformation.

The Sirtfood diet is based around a family of proteins called sirtuins, which are involved in a huge number of bodily functions, such as regulating your metabolism. By eating foods that are 'sirtuin activators', the creators claim you'll increase your body's ability to burn fat, resulting in rapid weight loss of up to seven pounds in one week.

While the Sirtfood diet sounds tempting – especially given the celebrity association with Adele's weight loss – any diet promising fast results should ring alarm bells. Sirtuins are proven to play a role in reducing inflammation, regulating your internal body clock and preventing ageing, but their mechanism is not yet fully understood.

With advice from qualified nutritionists Naomi Mead and Jenna Hope, we look at the Sirtfood diet pros and cons – including how it works, which foods are included, and risks to be aware of:

What is the Sirtfood diet?

Created by UK-based celebrity nutritionists Aidan Goggins and Glen Matten, the Sirtfood diet is based around plant-based foods they call 'sirtuin activators'. They're said to contain compounds that stimulate the SIRT1 gene – dubbed 'the skinny gene' by the diet's creators – which boosts the level of sirtuins in the body. The result? You'll 'switch on your body's fat-burning powers, supercharge weight loss, and help stave off disease,' the duo claim.

Kale, strawberries, onions, walnuts, and extra virgin olive oil are all listed as 'Sirtfoods' on the plan, and drinks like coffee, green tea, and red wine are also encouraged. While there are potent health benefits associated with many of these foods, the Sirtfood diet has tight calorie restrictions – in the initial week, calories dip as low as 1,000 per day.

That's not the only reason the Sirtfood diet remains highly controversial. There's little evidence for the role of sirtuins in humans. Even though scientists have been studying these proteins for the past few decades – mostly focusing on age-related diseases, inflammation and longevity – with promising results, their work is limited to test tube and animal experiments. Still, that hasn't stopped famous faces from trying the diet themselves.

While Adele acknowledged her svelte appearance on NBC's Saturday Night Live in October 2020 – 'because of all the COVID restrictions and the travel bans, I had to travel light and only bring half of me – and this is the half that I chose,' she joked – the artist still hasn't revealed whether the Sirtfood diet was part of her transformation. But the question mark around Adele's weight loss method hasn't prevented the likes of Pippa Middleton and Conor McGregor from jumping on the Sirtfood diet bandwagon.

What can you eat on the Sirtfood Diet?

The Sirtfood diet is built around a list of 'Sirtfoods'. The first phase lasts a week, and involves eating just 1,000 calories per day – one Sirtfood-rich meal and green juices – for three days, followed by four days of two Sirtfood meals and two juices a day, totalling 1,500 calories.

The second phase, dubbed the 'maintainence phase' lasts two weeks, and involves eating Sirtfood-heavy meals and juices. After this phase, the focus is on 'sirtifying' your diet in the long-term – ie, incorporating more Sirtfoods into your diet.

The book's top 20 Sirtfoods are listed as:

  • Extra virgin olive oil

  • Capers

  • Red onions

  • Parsley

  • Kale

  • Walnuts

  • Strawberries

  • Chilli

  • Soy products

  • Cocoa

  • Green tea

  • Coffee

  • Medjool dates

  • Red chicory

  • Lovage

  • Rocket

  • Celery

  • Buckwheat

  • Turmeric

  • Red wine

While foods recommended on the Sirtfood diet are generally nutritionally-dense, the diet's quick-fix approach has been heavily criticised by experts, given its extreme initial caloric restriction. 'Eating 1,000 calories per day is not recommended in order to support adequate nutrient intakes, energy function, a healthy relationship with food or optimal physiological functioning,' says Hope. 'It's hardly enough energy for a toddler, let alone an adult.'

Does the Sirtfood diet work?

There's no convincing evidence that the Sirtfood diet works better for weight loss than any other calorie-restricted diet. Unfortunately, even if you lose seven pounds in the first week of the Sirtfood diet, much of that will be 'water weight'. Water is expelled as your body uses up stored glycogen. Once you begin eating normally again, your replenishes its glycogen stores, and the weight returns.

What's more, calorie-restrictive diets slow your metabolic rate, which means you burn fewer calories each day. This effect can persist long after the diet ends. And that's not all. Other side effects include 'tiredness, hunger, fatigue, impaired nutrient intakes and low mood,' says Hope. 'Furthermore, due to the low-calorie element, the diet is unsustainable for a prolonged period of time and may contribute to an unhealthy relationship with food.'

There is limited evidence on the Sirtfood diet in general. The only known human trial was conducted by Goggins and Matten in London, and involved 40 individuals undertaking the first phase. It's widely cited throughout their book, The Official Sirtfood Diet, as evidence of its effectiveness, however the results have not been published in an academic journal.

All but one participant carried out the trial until the end. The remaining 39 participants lost an average of 7lbs (3.2kg) over the week. Their muscle mass was either maintained or increased, and they also reported feeling and looking healthier. The trial has several limitations, including:

🍽 Small sample size

Critics question whether it's good scientific practice to extrapolate the findings from 39 individuals onto an entire population,' says Mead. 'There are talks of larger clinical trials, but until these take place this question mark won't go away.'

🍽 No long-term results

'As there was no reported follow-up to this 7-day trial, we don't know whether the participants' maintained this weight loss long-term,' says Mead. 'Did they put the weight back on when they returned to eating a normal diet, without calorie restriction?'.

🍽 Sample bias

'The trial was performed on gym-goers who were already healthy and exercising regularly,' says Mead. 'A more representative sample of the general population would give a truer picture of how effectively the diet could work for the average person.'

🍽 No control group

'How can we be certain that the weight loss observed was due to the effects of sirtfoods, and not simply from calorie restriction?,' Mead asks. 'Because a control group wasn't used, we can't draw firm conclusions on whether Sirtfoods were a significant contributory factor to the weight loss.'

Is the Sirtfood diet healthy?

Incorporating more Sirtfoods into your diet is no bad thing. 'There is no denying that the advice to eat more plant foods high in fibre, vitamins, antioxidants, phytochemicals and polyphenols is good health advice,' says Mead. 'However, we need larger-scale human studies, before we can make any firm conclusions on the role these particular foods can have on specific aspects of our health.'

However, should you follow the Sirtfood diet, with its restrictive food groups and low-calorie phases? For our experts, it's a resounding no. 'Focus on a nutrient dense, well-balanced healthy diet in order to promote long-term sustainable weight loss,' says Hope. 'There is limited scientific evidence to support the Sirtfood diet for weight loss and therefore there are far more sustainable options available.'

Last updated: 15-02-2021

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