‘Am I going to survive this?’ is the single thought running through my mind as I stare down at the thick, lurid-green smoothie sat in front of me.

Following in the footsteps of broadcaster Zoe Ball and TV judge Rob Rinder, I'm here in Quinta da Maravilhas, in Portugal's Algarve region, for a week-long stint at Juicy Escape – the latest wellness retreat to garner celebrity approval.

Along with my fellow guests, I'll spend the next seven days sampling a wealth of different fitness and wellness activities in an attempt to relax and reset.

The only catch? I'll be fuelled only by Juicy-approved juices and blends.

Founded a decade ago by British wellness guru Jason Vale (or the 'Juice Master', as he's come to be known), Juicy Escape operates retreats here in the Algarve, as well as central Portugal (Juice Oasis) and Turkey (Juicy Mountain).

The programmes are designed to help guests reconnect with healthy habits, while hopefully shedding a few unwanted pounds along the way. 

But unlike other retreats, the emphasis here at Juicy Escape is firmly on having fun; 'when you arrive, we want you to feel like a child again', their website reads.

Indeed, with all manner of activities taking place throughout each day, from pickleball and padel to 80s-themed spin classes and sunset yoga, it’s no wonder Juicy Escape has earned the nickname ‘Europe’s healthiest playground’.

And unlike similar state-of-the-art wellness offerings, I'm relieved to find that the atmosphere is far from pretentious.

Despite top-tier facilities, luxurious accommodation – and praise from the rich and famous – there's an easygoing feel to the set-up.

I quickly settle in with my fellow participants, as we ready ourselves for the challenge of the week ahead.

But before I can get stuck into my jam-packed schedule, there’s another small matter to attend to: my diet for the coming week.

While taking part in swimming, yoga and boxing classes, I am to subsist on a cocktail of fresh juices and blends, expertly concocted to help me unwind and shed some unwanted weight.

And my first drink of the week, the Green Super Smoothie, is a thick, sage-coloured mix of apples, spinach, kale, lime, celery, avocado and wheatgrass.

I almost wince with the first sip – the taste of wheatgrass is almost overwhelmingly strong.

I have to remind myself, though, that every ingredient has been chosen for a reason.

While not always tasty, these ‘blends’ are far from random in their makeup – but are instead expertly balanced to provide the nutrients I’ll need throughout the week.

According to Vale, drinking these juices frees the body, providing it with ‘the nutrients, the space and the time to do what it ordinarily wants to do.’

Living primarily on juice is certainly a gear shift. But despite my initial scepticism, I’m surprised by quite how invigorated I feel.

Certainly, there are moments when I crave even a morsel of chocolate, or a little packet of crisps – but as I bounce through morning trampolining with my fellow rebounders, I’m struck by how much energy I seem to have, and the new-found spring in my step.

It's this sense of wellbeing that’s central to the retreat’s philosophy.

While weight loss is certainly a draw for many participants, the retreat aims to encourage broader lifestyle changes, too.

‘Don’t treat this as something on the way to something good,’ says Vale. ‘A lot of people play the “I’ll be happy when…” game.

‘If you say: “I’ll be happy when I’ve lost the weight”, what you’re really saying is you’ll be miserable until that happens. The idea while you’re here for the next seven days is that you’ve all got a playground to play in.’

And there’s plenty to keep us occupied.

Between volleyball matches, sunset yoga sessions and walks along the retreat’s private beach, I find myself spoilt for choice.

Towards the end of the week, however, the cleanse starts to feel more challenging, and I retreat to my igloo-style cabin, ‘Wondrous Wave’, which overlooks the onsite lake and surrounding countryside.

The sweeping views over the rolling green hills provide a welcome distraction as my remaining days tick by.

It is all worth it in the end, though. By the end of the week, I’m thrilled to find I’ve lost almost four pounds, and have dropped two per cent body fat.

More surprising than the numbers, however, is how different I feel.

Somewhere between ambling walks along the beach and fast-paced games of padel, I feel my mindset shift. 

In addition to slowing down my usually busy brain, the focus here on fun and enjoyment has also filled me with a renewed sense of positivity and energy.

Yes, it’s a juice cleanse. But it’s also a reminder of how good life can be when you put yourself first – and have a bit of fun.