Hotel Hit Squad: Glass House has plenty of treatments to feed the soul – but you might have to sneak out to Nando’s

Do the Roaring Twenties signal the end of the Whimpering Teens? I couldn’t help wondering, listening to the robust grumbles of disapproval over tomato soup for dinner at a luxury detox weekend in Upminster. Glass House, a recently opened white-cubed retreat, jutting from isolated Essex green fields, takes its low-carb vegan food philosophy seriously. However, the problem is that pesky guests like me don’t.

Meals – set in the glittering dining room, all wine glass chandeliers and honey-coloured sunsets streaming through the windows – were a controversial affair. Ladies on the juice diet chirped enthusiastically over their blueberry and kale smoothies. Many of us guests who had booked on the higher-calorie Equilibrium menu, who were expecting to eat healthily but substantially, were more than a little taken aback by the strictness of the portions of quinoa-speckled salads and avocados gauntly wrapped in wisps of courgette. One couple even snuck out to Nando’s for dessert on the first evening.

Glass House has hit on an intriguing quiet revolution that is coming to the health retreat industry; the number of us who are checking in, in search of life-enhancing reboots, rather than game-changing transformation – even when we can still feel the sickly residue of champagne and Terry’s Chocolate Orange seeping from our pores after new year.

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Apart from its gruelling food menu, which is better suited to guests who are looking to drop a dress size, the Glass House retreat is hard to fault. The place smells like one giant Jo Malone candle, so that you don’t so much walk as ethereally glide through the hallways. With a wooden spliced sculpture here, a gently psychedelic watercolour there, the light-touch decor has skilfully strong character. And, from the dusky, velvet sofa-cosseted lounge, to the bedrooms decked out in cool grey fabrics that contrast with white orchids, the interiors are almost scientifically engineered for deep relaxation.

The activities are outstanding. Mornings usually start with a glass of warm water with lemon followed by a crisp country walk, as the sun creeps up hopefully through the corn rows of the surrounding fields. After breakfast (not so much a helping as an Instagram-artful sprinkling of granola, in my case) there is usually an array of high-cardio morning fitness classes, from boxercise to toning and water aerobics.

Alternatively, guests can saunter to the bijou spa, with its heated pool, and (very) snug sauna, before indulging in one of the treatments. The quirkiest is the cryo chamber – a therapy popular with athletes and celebs for its fat-burning, anti-inflammatory effects. Those brave enough spend five minutes clad in their swimwear and a pair of mittens in the -85 °C to -110 °C (-121 °F to -166 °F) hut, will come out pumping with endorphins (though it takes several sessions to see a reduction in cellulite).

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The massages are also divine, especially the Glass House heaven signature, on a hydrotherm flotation bed, which makes you feel like you’re drifting gently along the ocean, followed up with a skin-plumping, peptide-rich Elemis facial. Given the sparse lunches – a juice, or a salad/vegetable dish if you are on the Equilibrium menu – hunger pangs can start to set in by late afternoon. Although this is the point at which some retreated to their rooms to binge on Netflix while trying not to dwell on the lack of accompanying popcorn, I found it was better to keep myself busy with a class. There is usually a yoga or stretch session, perfect for focusing the mind away from the growl of an empty stomach, and unwinding tin-man muscles and tendons.

For those with large appetites, dinner is as unsatisfying as it is eagerly anticipated – but by consolation there is usually something stimulating going on afterwards to nourish the soul.

When I was at Glass House, on one night there was a sound bath session, where, swaddled in blankets, we meditated to 432hz glass-pings in line with the earth’s frequency (in contrast, most commercial music is tuned to a more disharmonic, stress-inducing 440hz). On another, we were treated to a crash course in essential oils as an alternative to modern medicine when it comes to everyday ailments (peppermint on the temples for headaches; eucalyptus for sinus trouble; clary sage for fertility issues).

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For all the niggles over the food, I left the Glass House retreat feeling ready to take on a new decade, after an exhausting 2019. I am also adamant that the mantra of my new year will be to pursue self-fulfilment rather than revel in virtue-signalling self-abnegation. Pass the cheese and crackers.

Two-day packages from £579; glasshouseretreat.co.uk