I I should probably preface what follows by saying that when it comes to the nebulous concept of "wellness", my feelings are decidedly ambiguous. Whatever battle the wellness warriors are fighting, I've historically been on the other side, nonchalantly tucking into a family bag of crisps and wryly swirling a glass of pinot gris like a mischievous teenager smoking a cigarette. However, the older I get, the less this attitude seems louche and bohemian and instead feels somewhat reckless. While I absolutely believe in body positivity and don't want a jade egg anywhere near my privates (or a candle that smells like them, for that matter), I also want to get past 3pm without slumping into a sugar and caffeine spiral and to fit into my jeans minus the sharp inhale.

The result is that I'm constantly fighting a battle between my entrenched bad habits and my attempts to claw back some balance, with corresponding loops of weight loss and gain. Although I'd consider myself a healthy-ish person in my down time - I do high-impact cardio classes three times a week, follow a pescatarian diet and know my kimchi from my kombucha - as soon as a dinner invitation or plane ticket wafts my way, my intentions disappear faster than a negroni on a Soho House rooftop. A festive season consisting of a doughnut-filled trip to the States, back-to-back roasts and an epic New Year's Eve feast washed down with champagne had indulged all my vices and left me bloated, with skin as mottled as a seal's and carrying a few extra kilos under my straining belt.

All of this means that as I speed across the Austrian border from Ljubljana Airport to Lake Wörthersee and the legendary Original FX Mayr clinic, I'm more than a little nervous. Founded in 1976 and inspired by the Austrian physician Dr Franz Xaver Mayr, who developed a treatment plan for post-surgery patients based on resting the digestive system and reversing the process of "auto-intoxication" that we induce by ingesting the wrong things, the clinic offers a 21-day "cure" programme based on a combination of medicine, nutrition, exercise and awareness (guests can complete all or part of the programme at the clinic - I'm here for a week). It's perhaps most famous as the inspiration behind the 5:2 method, whose followers consume less than 500 calories for two days a week and eat normally for the remainder.

The "intermittent fasting" principle that underlies both this and the cure, whereby you have all your meals within an eight-hour window and fast for the remaining 16, has garnered a bevy of gym bros, Silicon-Valley CEOs and model-influencers of late - Elon Musk, Chris Hemsworth, Rosie Huntington-Whiteley and, of course, Kim Kardashian have all endorsed its benefits, which in addition to weight loss are said to include the slowing down of the ageing process and the growth and development of brain cells and nerve tissue. As I sit down for breakfast on my first morning, the ambience is rather less starry - half of my fellow guests have already succumbed to the uniform of robes and hotel slippers and the decor is more 1970s B&B than sleek and sci-fi. That said, it's cosy and homely, and I'm happily staring out the window at the low-hanging clouds that skim the icy lake when my food arrives, at which point I stare down in horror.

I'm greeted by a miniature milk-bottle filled with sheep's yoghurt and a tough buckwheat roll, designed to encourage you to chew each mouthful at least 25 times (did you know that people who chew their food properly are on average 15kg lighter?). I pick up a Borrower-sized teaspoon and tentatively start nibbling while trying to observe the rule for silent dining. The intention is to enable slow, mindful eating that allows you to feel full faster (the brain takes around 20 minutes to get the message that food has arrived) and reduces the stress that inhibits proper digestion. Lunch follows the same pattern but swaps the yoghurt for vegetable soup, whereas dinner is a thin vegetable broth - in total I'll be consuming a miserly 400 calories a day.

However, the Mayr cure is "not a weight-loss diet, but a health diet", as my brilliantly no-nonsense doctor later tells me. Each guest gets their own doctor who tailors the cure to their needs and checks in with them every other day to recommend additional treatments and monitor progress. After chatting about my goals and lifestyle, Dr Muntean-Rock massages my abdomen and diagnoses me with bloating and inflammation in the gut and water retention in the lower legs before prescribing me a range of treatments to complement my cure. She explains the core tenets of the Mayr method - cleansing and detox, resting the mind and digestive system, training ourselves to eat more mindfully, following a regular rhythm with our exercise, sleep and mealtimes, and conscious abstinence - and that the goal is to help reset the overloaded digestive system, adding that recent scientific breakthroughs suggest that many of our health issues may stem from imbalances in the gut.

Having been reassured that the crippling headaches I've been suffering with for two days are not signs of an impending aneurysm but in fact caffeine withdrawal, I skip off for a series of screenings. A metabolic analysis during which I breathe into a plastic tube reveals that I actually have a fairly high metabolism, but that it's running in extreme-sugar rather than fat-burning mode, likely thanks to all that champagne. A body composition measurement, where I lie on a table with wires attached to my fingers and toes while electrical currents run through my body, shows that I contain approximately eight per cent more fat than a Lindt Lindor ball. This seems apposite given the number I annihilated over the Christmas break but is not, I learn, a healthy proportion for a human being. I have an applied kinesiology test where vials of substances such as lactose, egg and gluten are rested on my stomach and my muscle reaction is tested to identify intolerances - I'm sceptical of what seems like sorcery, but the results line up with a later blood test.

As for the fasting, although going to bed hungry is hard, I don't find it as much of a chore as I'd anticipated and start to appreciate the flavours of everything laid in front of me much more intensely. One morning I'm served a soft-boiled egg alongside my buckwheat roll and have a frankly indecent moment tonguing its velvety folds and making obscene noises - it's a platonic egg, the egg to rule all eggs, perfect in its sheer eggyness. I even start to convince myself that the dreaded Epsom salts I down each morning taste not too dissimilar to a bitter G&T. However, I'd been warned about "fasting crisis" - the point where your body runs out of its usual energy stores and sends out alarm signals before it begins burning fat - hitting on day three, and sure enough I wake up feeling as wobbly as if I've had five shots of tequila and then attempted a 10k run. I have to negotiate whether I have enough energy to walk across the room or dance to Ariana Grande while brushing my teeth and spend most of the day trying not to collapse into the nearest wall or cry.

However, the next morning I practically explode out of bed, riding a crest of pure energy that doesn't dissipate for the remainder of the week. Relieved, I start to revel in the luxurious line-up of treatments that gently unspool the issues of which I'm aware of, tease out some I've ignored and boost my ammunition against others. Osteopathy and shiatsu sessions unknot the tension in my shoulders and back brought on by days hunching over a laptop, while a lymphatic drainage massage visibly reduces the bulk around my ankles. I sink into an alkaline detox bath, read a book in bed while a hayflower wrap is pressed to my liver, and nearly fall asleep during a reflexology head massage. I huff oxygen-depleted air through a mask to stimulate mitochondria (energy-producing cells) growth, spend an hour smothered in collagen and being pummelled by a pair of electronic foam trousers to combat cellulite, and have pure medical oxygen inserted into my posterior following colon hydrotherapy, simultaneously the most undignified and decadent thing I've ever done. Meanwhile the afternoons begin with mellow hikes into the surrounding forest and end with group guided meditations, punctuated by the snores of those who have relaxed a little too hard.

At the start of my fifth morning the four-pack of brioche buns that was masquerading as my waistline has halved to a two-pack and I've lost 2.5kg, as well as most of the bloating and inflammation. A week and a half later and back on home turf, I've continued to observe the cure principles and lost another 5kg - but more than that, I feel clear-headed, energetic and surprisingly, more creative. Although I'm looking forward to phasing back into a more regular diet plan - indeed, continuing to fast at this level indefinitely would actually weaken the digestive system and result in muscle being burned off as well as fat - I'm also hoping to implement some of what I've learned into my daily life: skip dinner as often as you can, no raw veg past 4pm, take time to savour your meals, don't punish yourself for the occasional indulgence. The whole experience has been non-judgemental and reassured me that my existing systems are working well, while giving me the tools and information to make better choices as to what I feed them - and at the comparatively young age of 31, it's a privilege to have the time to make those changes now rather than trying to fix issues at a later stage. While I wouldn't say it's made me a wellness warrior, I might put the pinot down a little more often from now on.