Sirtfoods: Is This Diet a Legitimate Approach to Healthy Weight Loss?

 

If you've heard the term 'sirtfoods' buzzing about recently, it's likely because of rumours that Adele employed the diet as part of the regime that is behind her recent weight loss.

While this has never been confirmed by the superstar, 32, you might be wondering what the deal actually is.

 

What is a sirtfood?

Short story: sirtfoods include kale, dark chocolate, olives, red wine, blackcurrants, kale, parsley and capers. The claim is that they’re able to promote fat burn, helping you lose weight. Here's a more complete list:

• Bird's eye chillis
• Buckwheat
• Celery
• Capers
• Cocoa (dark chocolate)
• Coffee
• Extra virgin olive oil
• Green tea
• Kale
• Medjool dates
• Parsley
• Red chicory
• Red onion
• Red wine
• Rocket
• Soy foods (like tofu)
• Strawberries
• Turmeric
• Walnuts

Before we get on to if there is any evidence behind the hype, here’s your sirtfood 101. The ‘sirt’ part refers to sirtuins, a class of proteins within our body. 'Foods don’t contain sirtuins, but they supposedly contain compounds that activate sirtuins,' says Dr Kushal Banerjee, researcher at Harvard Medical School. All well and good, but what the hell do sirtuins actually do?

Well these proteins have been on the scientific radar for around 10 years and have until now mainly been the subject of anti-ageing research. There are seven of them, but SIRT1 is the one we know most about.

You’ve probably never given much thought to the mechanics of weight loss. Fewer calories equals falling pounds, right? But slap bang in the middle of that process are sirtuins – the middlemen that, when ‘switched on’ by calorie restriction or exercise, are key players in the resulting fat loss. 'When you restrict calories, SIRT1 is activated and it tells the body to switch from using glucose as energy to breaking down fat and using that instead – rather than storing it as love handles,' explains Banerjee.

Can sirtfoods boost your metabolism?

Moreover, sirtuins can have an effect on both metabolism - 'Sirt1 speeds up the metabolic rate and therefore the rate at which your food is burnt,' says Banerjee - and on the composition of the body’s fat.

Qiang Tong, associate professor at the Baylor College of Medicine, Texas, is an expert on sirtuins' influence on brown fat tissue – the ‘good’ type of fat that keeps us warm and which we burn when we’re cold (white fat is a storage depot, aka love handles). 'Obese people tend to have less brown fat than leaner people. The thinking is that sirtuins can help activate more brown fat and help keep people lean' – a theory confirmed by a 2012 study published in the scientific journal.

So this much we know: sirtuins play a role in weight loss and they’re activated by exercise and calorie restriction. The question everyone is asking, however, is whether sirtuin-activating foods have the same effect?

Enter: the Sirtfood Diet

This is the proposition put forward in The Sirtfood Diet, a 2016 book by nutritionists Aidan Goggins and Glen Matten, set to become the dieting bible of 2016. Before we all set up camp at our nearest Waitrose olive counter, however, it might be worth investigating the science of sirtuins just a little bit deeper.

According to the experts, the picture is complex. 'There’s a big jump between eating some kale and activating a sirtuin response,' warns Matthew Hirschey, assistant professor at Duke University Medical Center in North Carolina.

Does the Sirtfood Diet actually work?

'We don’t yet have the evidence that certain foods activate this more than others – or to which specific tissues they’d be beneficial,' says. 'Even if sirtfoods do trigger weight loss, the sheer quantity we’d need to eat may be unmanageable.' He points to resveratrol, the polyphenol in red wine and the most well known of all sirtuin activators.

Resveratrol shot to fame in 2003 when a laboratory of scientists run by David Sinclair discovered that this compound, found most commonly in the skins of red grapes, mimicked the effects of calorie restriction and activated sirtuins that prolonged the life of cells. Hence the ‘red wine helps you live longer’ school of thought that’s become increasingly popular bandied about at the pub.

But, Hirschey points out, 'The majority of studies have been carried out using experimental systems in the lab, mostly on mice or fruit flies, or directly into cells. To get resveratrol's anti-ageing effects from red wine, you’d have to drink up to 40 litres a day.' Which makes you wonder how much kale you’d need to be packing in order to lose weight.

The nutraceutical industry is already one step ahead, with resveratrol supplements already available. Be wary, however, of just popping some sirt-activating pills or lacing your smoothies with resveratrol powder, as one study from the University of Copenhagen has indicated that increased supplementation of the antioxidant counteracted the good effects of exercise.

'Some literature shows that certain cancers have sirtuins that are activated,' adds Hirschey. 'This is why it’s problematic to tie labels to things – what’s good for one tissue might not be good for another.'

All this just demonstrates how confusing the science of sirtuins actually is, and how early we are in our understanding of how they impact not just weight loss, but wider health.

Nutritionist Kim Pearson spells it out quite nicely: 'All of these so-called ‘sirtfoods’ are simply polyphenols, and you really can’t go wrong with them. If you tell people to eat more kale and replace coffee with green tea, and combine this with exercise and an all-round healthy diet, you’ll probably see results.But will it be enough to activate metabolic pathways within your body? Unlikely.'

What’s more, she points to the fact that most of these sirtfoods are staples of either the Mediterranean or Eastern diet (things like olive oil, capers, green tea and turmeric), suggesting that research around sirtuins simply 'reinforces belief systems and natural remedies we’ve known to work for centuries.'

Look, one thing’s for certain: eating sirtfoods isn’t going to do you any harm (unless you’re mainlining red wine – that bit about 40 litres a day was not a challenge). But if it’s specifically a sirt-activated response you’re after, science says exercise or calorie restriction are the surer bets.

Are there any other benefits to Sirtfoods?

Sirtuins also have a hand in a host of other health benefits. Including…

Sleep

Activating sirtuins helps your circadian rhythm, ensuring you produce the hormones for sleep and waking when you’re supposed to.

Diabetes

Sirtuins make cells more insulin sensitive, which means they can remove more glucose from the bloodstream. Seeing as insulin resistance is the precursor to both diabetes and weight gain, this can only be good news for your waistline.

Memory

Turmeric has been shown to improve short-term memory and protect against cognition problems. Pack into your morning juice for a brainier start to the day.