In daily life, the hunger of the soul is often confused with the need to eat.” So said Dr Otto Buchinger, the guru behind a no-frills, therapeutic-fasting clinic in Germany. I am burnt out and my feeble attempts to fast for just two days a week on the regime du jour, the 5:2 diet, have proved futile, so I have decided that Buchinger’s 10-day retreat with strict routines and a 250-calorie-a-day fasting plan is the way forward.

On booking, the clinic advises that for a few days in the run-up to my visit, I refrain from meat, caffeine and alcohol. The day before I am due to fly out, I haven’t quite stuck to its pre-fast diet, so I swing by The Juicery in Marylebone to pick up some potent antioxidant green juice to see me through the next 24 hours.

Day 1

An hour’s drive from Zurich, the clinic is a complex maze that’s one part sanatorium, two parts John Pawson-esque minimalism, with incredible views of the majestic Lake Constance (pictured above) – obscured by a colossal grey cloud that spits rain until noon. After being shown to a sparse, white room, I have my welcome consultation with Dr Drinda. It lasts 30 minutes and comprises a blood-pressure check, weigh-in and a lengthy interview on my emotional and physical state, followed by a lecture on my overenthusiasm for my favourite source of resveratrol (quelle surprise). My last supper is rice and vegetables, which I have in my room, looking out at the still, dark lake. I practise 20 minutes of transcendental meditation and hop into bed.

Day 2

I head to the nurse’s office – pot of urine in one hand and cup of Rooibos tea in the other. She sets out my schedule for the coming days: “The body likes routine, so you will see me every morning at 8am to check your blood pressure and weight. At 11am you’ll have apple-skin tea and every other day this will be accompanied by an enema. From noon, you can go to the main house for your first of two daily vegetable broths, and by 1pm I would like you to do a liver pack in your room.” As I look at her with confusion, she explains that a liver pack is a damp cloth and a hot-water bottle placed on the abdomen to increase the circulation, draw out toxins, and kick-start the metabolism. 10am It’s time for my personal-training session with Mrs Veit, a diminutive lady with a no-nonsense attitude. TRX bands hang from the ceiling, while medicine balls, bosu balls, weights and an array of cardio machines line the glass windows that look out over the lake. We embark on a challenging set of circuits: squats, lunges, burpees, Russian twists, planks and mad dashes on the treadmill. It’s hard, especially with only tea with lemon for breakfast.

11.15am – I was feeling fragile when I arrived, but as I collapse into the chair for my consultation with Dr Van Houten, tears of exhaustion well up. She is not surprised: my lifestyle is wreaking havoc on my insulin levels and hormones. “I want you to do virtually nothing while here. Your prescription is just fasting, mountain air, rest, plenty of hot tea and the daily hike [pictured top right] – Otto Buchinger was a firm believer in mountain walks.” After some persuasion, she agrees to a personal- training session each day.

1pm – After taking Glauber salts (to help with bowel cleansing), I eat the tasteless vegetable broth with a few leaves of fresh coriander in my room. Next, I head for the lobby, where the assembled group is divided into advanced, intermediate and beginners, for a two-hour hike in the surrounding countryside and through the town of Überlingen. I opt for the advanced group and pace up the hills ahead of the pack. The stunning views do a marvellous job of calming my mind. Back at base, I have a Thai massage with Dr Kuhner, during which I keep my clothes on and lie on a soft mattress on the floor while he performs a combination of acupressure, gentle twisting and stretching out of my limbs. His pressure is perfect. I meet my nurse back in my room for the liver pack. She lays it on my stomach and I lie back and meditate, which is enormously relaxing.

7pm – I spend half an hour in the sauna. It is mixed sex and everyone is naked. I am not sure that makes it the most calming of experiences. 9pm The hunger pangs are so intense I head into the corridor to see what I can scavenge. I plead for another portion of soup and but am adamantly told no – the next best thing is the apple-skin tea. I purloin several pots.

9pm – The hunger pangs are so intense I head into the corridor to see what I can scavenge. I plead for another portion of soup and but am adamantly told no – the next best thing is the apple-skin tea. I purloin several pots.

Day 3

After a terrible night’s sleep, I wake to a thumping headache, a typical side effect of detoxing. As I sip my herbal tea, I tell the nurse that I am starting to feel weak. She takes my blood pressure, which has plummeted, and hands me half a cup of apple sauce with a dollop of honey. “Days two to four are always the hardest,” she says. “Let’s get you back in bed.” But not before an enema. Afterwards, I have some soothing apple-skin tea, the nurse brings me a hot-water bottle and I curl up under the covers.

1pm – I make my way to my Ayurvedic massage with Mrs Spitz. It’s an almond- and sesame-oil treatment, which is wonderfully gentle and relaxing. At lunch, because of my low blood pressure, I’m allowed two bowls of broth. It doesn’t feel like quite enough sustenance for the optional daily walk, however. We hop in a bus and head for Haldenhof for a brisk four-mile woodland hike. It’s invigorating but tough – and completely wipes me out for the rest of the day.

Day 4

I wake with a thick, bitter-tasting residue on my tongue, another sign of detoxing. My energy levels appear to be on the rise. Ketosis has kicked in – my body has switched to a more efficient way of burning its fat reserves to satisfy its basic energy needs. The mirror shows that my once-bloated face looks leaner, my skin is glowing and my eyes are bright. A visit to the nurse reveals I have lost 1.8kg. She says that most of it is water. My blood pressure is stable and I’m looking and feeling better.

9am – My one-on-one personal-training session with Mrs Dohner, the most sought after of all the workout leaders, is hard: more circuits with some plyometrics. She has no mercy – there’s hardly a second to catch my breath and by the end I am exhausted.

2pm – After vegetable broth in my room, I set out for another group-guided, 90-minute hike to a neighbouring village, which takes us through forest, farmland and fields of cows. I am starting to feel pretty good. My stomach grumbles aggrievedly, but I feel alert. I round off the day with a liver pack and a traditional Thai massage from Mr Kuhner.

Day 5

My trip to the nurse gets the day off to a good start: she is impressed at the rate I am losing weight (the total so far is 2.2kg) and by my positive attitude.

9am – Today’s 55-minute gym session focuses on isometrics – tensing my muscles without moving any part of my body. It’s great for targeting specific muscle groups, such as the core abdominals with the plank and obliques with side planks. I do 10 minutes of planking in total, holding and resting for alternate minutes. I’m smiling through the pain.

10.30am – I’m well and truly into the swing of things, and my body is no longer crippled by hunger pangs. I stop by the garage, collect a mountain bike, set my workout playlist and bomb around the lake for 90 minutes. I have my pre-lunchtime broth, then it’s time for some pampering in the salon. I opt for a two-hour gold anti-ageing facial using Deynique products. It is top-notch and leaves my skin glowing and firmer. I feel amazing. Supposedly when patients fast, the stress hormones decrease and serotonin levels rise, resulting in a “fasting high”. When I arrived, my brain was whirring, but now I have clarity. 5pm My deep-tissue massage takes place in the building that houses the wet spa. Sadly, I don’t think the 50-minute session even touches the sides when it comes to my stiff back, neck and shoulders. Nevertheless, it is pretty thorough – more medical than pampering. Since I arrived, my sleeping has improved, although the excess of liquid makes it quite hard to have a night uninterrupted by loo breaks.

Day 6

I wake up full of energy. Despite the meagre diet of herbal tea and two daily bowls of broth, my gym sessions and the daily walk are getting easier. My skin blemishes have also cleared and my face is radiant. In the evening I even add a yoga class into the mix. But it is for beginners, so doesn’t tax me enough.

Day 7

Again I wake up feeling sprightly. I decide to switch my daily gym session for a swim in the outdoor heated pool, followed by a stretch in the sauna. My hunger pangs have really died down. I am a lot less peckish than on any other detox I have ever done.

Day 8

So begins a two-day reintroduction to food – key for a smooth re-entry into normal life. The first meal is a large portion of apple purée. It seems vast. Lunch and dinner are a selection of rice, potatoes and grilled vegetables. The day’s intake only comes to 800 calories, but after a week of not eating, the portions seem enormous – a few bites and I’m full.

Day 9

Breakfast now includes a choice of yoghurt or porridge, while lunch extends to tofu and crudités. I am also allowed some chicory coffee with almond milk – a real treat. Filled with energy, I am buzzing. Before my personal-training session, I run for half an hour on the treadmill. Then I cycle round the lake and top it all off with a group Pilates session – which is significantly better than the yoga class. In the afternoon, it’s time for the signature Buchinger walk. The combination of good old-fashioned exercise, mountain air and organic food (when I get it) is simple but incredible.

Day 10

I make one last visit to the nurse, for a weigh-in and check-up. She is impressed by my weight loss and when she reruns the checks she did on the first day (on my thyroid and hormones), everything is as it should be. We finish up with a vitamin A and B intravenous drip, which gives me a final pep-up. I am raring to return to the urban jungle.

The Bottom Line

By day two, I was in tears and dying to go home. I felt cold, dizzy and frankly a little depressed – I missed the textures and flavours of food but, more importantly, those rituals that come with eating. But as it turned out, the fasting allowed me to appreciate the joys of meals afresh. By day four, the benefits of the detox started kicking in and I was on a “fasting high”. The dark cloud lifted, as did the bloat from my face and midriff. Over the next few days, my mood and energy soared and, without meals to punctuate the days, I found myself meditating regularly, and enjoying the long walks.

Rarely have I been on a detox where lack of food was so bearable, nay, enjoyable. As my hunger pangs evaporated and my euphoria soared, I experienced no cravings for sugar or wine and my passion for physical exercise was restored thanks to energising, inspiring hikes around that magnificent lake. My final weight showed a loss of 5.5kg. But far more valuable is the sheer lightness in body and mind that came as a result of the process – I felt like a new person. Ten days was a perfect reboot. Would I go back? Absolutely: I’ve already booked in for a fortnight in five months’ time.