I should be miserable I’d been cautioned: Watch out for day three. That’s when the demons begin to rage. I’m on a medically supervised 10-day fast that promises to help me shed some weight while also futureproofing that newly slimmed-down body against aging. Worth the odd demon or a pang or two, then.
Indeed, I’m a bit hungry—but that’s not surprising, given that I’ve consumed little more than tea, juice and soup over the past 48 hours. But I had been anticipating far worse, as several friends, all veterans of the Buchinger Wilhelmi process I am undertaking, had warned me. The real challenges in forgoing food wouldn’t be simple hunger, they said. “Fasting isn’t the hard part,” said one. “It’s the emotional side. I usually spend the third day curled in a ball in my room, weeping. Everything you repress just comes out, all at once.” A second moaned about the physical side effects on day three for her: throbbing headaches, a furry tongue and dry skin, all because the toxins her body was purging began to crest, she said, wide-eyed. The consensus was that I’d feel, generally, dreadful—not just hungry but also sad, aching and exhausted, likely confined to my bed, wakefully toggling between napping and fretting. Yet another confided that it was day three when the risk of cheating peaked. She’d heard that folks usually skulk out the clinic’s back gate and into the nearby town to scarf down a furtive frankfurter or two to offset the gnawing pains.
Instead, I feel fine.
More than fine. Remarkably, I feel absolutely dandy. I’ve no physical problems whatsoever; in fact, I’m swimming 50 laps in the pool here at the Buchinger Wilhelmi spa every afternoon, and the only reason my eyes are watering is the troublesome pollen. I miss chewing, for sure, and I’m not partial to some of the broth recipes: The mere mention of turnip evokes Dickensian deprivation, though the watery tomato is bright-flavored and delicious. But I haven’t cheated, despite deliberately wandering into town yesterday morning to tempt myself with the smells of fresh-cooked sausages. I took a deep breath—delicious for sure, but I was happy to eat with my eyes.
Either I’m too two-dimensional to be troubled by deep thoughts or I’m one of the lucky ones, sailing straight from eating three meals daily to the Zen state of semi-starvation without detouring down a physical and emotional rabbit hole. I’ve arrived, instead, at 200-calorie nirvana, where the body, now short on fuel, is forced into overdrive. With my metabolism working harder to produce energy, I experience a new level of strength and mental clarity. I am Superman without the blue tights. In fact, the only challenge for me is my sleep. Usually, I slumber deeply and soundly anywhere, so it’s strange to find myself so fitful, with bouts of deep rest punctuated by an unfamiliar alertness. Otherwise, I nod sympathetically as I try not to gloat when folks mournfully complain in the “feeding salon,” the lounge-like area where our non-meals are devoured.
It’s inside the salon that I first meet my fellow fasters on day one, at what passes for a welcome party at Buchinger Wilhelmi, on the shores of Lake Constance in Germany, just across the border from Switzerland. My fellow fasters are a motley bunch, drawn from across the world. I’m surprised the room is equally split between men and women. There are several first-timers like me: a Saudi couple, for instance, well-padded fiftysomethings who plan to stay for three weeks. Other newbies include a pair of friends, fit, middle-aged financiers who usually take an adventure vacation together each year, leaving their wives at home. Most of the room, though, consists of starvation pros, folks who’ve followed the Buchinger Wilhelmi method several times before. Typical is the French sculptor who’s back for a seventh stay. He became a devotee when his first stint allowed him to permanently shed the 40 pounds he’d gained after a car accident. Tall and gaunt, he looks to be in his late 60s or older; he’s come again, he explains, as an anti-aging effort. More than the chance to shed pounds, it’s this elusive promise that underpins the work at Buchinger Wilhelmi.
For this is no conventional fat farm. Forget face-lifts and fitness classes—it’s bouts of fasting that Buchinger Wilhelmi claims will offer a slimmed-down path to eternal youth, or something close to it, at least. Fasting, the staff preaches, will better safeguard your body against the forces of age. The focus here, though, is not only extending your life span but also improving the quality of whatever life you have, or what’s now known as your health span. The clinic’s practice aims to address a conundrum: How do we ensure our brains and our bodies remain in peak condition for our entire lives, bringing both quantity and quality of life in sync? Slash our daily energy source, Buchinger Wilhelmi posits, and the body’s metabolic switch is triggered. Deprived of easy fuel, our body’s metabolism instead turns to ketones, compounds produced from fats by our liver in a state known as ketosis, achieved by fasting at least 10 to 12 hours. There’s more afoot, too: During ketosis, the body starts to repair and reboot, helping bat away looming bad health. Per the clinic’s owners, eating 200 to 300 daily calories for several days, any time from your 20s to your 60s, isn’t just good for your waistline; it’s an investment in the well-being of seventy-something you.
There’s no hardship here, though. The clinic doesn’t resemble a traditional sanatorium but rather a five-star hotel. Scattered among several buildings on a steep hill, the rooms are decorated in muted tones and filled with tasteful, vaguely modernist furniture. One of the front-of-house staff is an alum of the Ritz Carlton in New York and proudly wears the lapel pin of Les Clefs d’Or, the elite cabal of concierges. There’s a hair salon but no conventional luxury hotel-style spa. Instead, the clinic offers two main medical complexes, where the doctors and nurses on staff perform their examinations, plus numerous treatment rooms discreetly tucked into various buildings, where guests can book everything from osteopathy and shiatsu massage to outré rituals like Chi Nei Tsang, a Chinese abdominal massage, to pass the time between non-meals.
And, yes, the food. Other than at the start and end of your stay, when you’ll receive delicious, low-calorie vegetarian meals to help ease your digestive system into and out of hibernation, there’s little to eat. (Don’t confuse fasting-induced ketosis with a ketogenic low-carb, high-fat diet.) Breakfast is herbal tea and a tiny saucer of honey; keep it for the day, the nurse advises, and eat it sparingly when you need some energy. Lunch is fresh-squeezed juice, cut with more herbal tea to reduce its calories. Dinner is the aforementioned broth. Such scraps—or drips—of food leave my digestive system effectively fallow, though there are regular enemas from the nurse just to make sure. She also checks my vitals each morning, reminds me to drink at least six liters of water a day (to stay hydrated and prevent gout) and comes to my room every afternoon to wrap my liver, one of the quirks of the Buchinger Wilhelmi process: After what passes for lunch, you’ll spend an hour or more in bed, swaddled like a baby with a hot water bottle pressed to your liver. Per the clinic’s theories, such cosseting helps boost the liver’s ketone production process.
The woman who helped formalize many such theories is Françoise Wilhelmi de Toledo, M.D. Trained as a conventional physician, she visited the clinic as a guest in her 20s—and never left. After marrying into the family, she became the medical director. Toledo is now the clinic’s head of medical research and lives in a sleek glass box of a house nearby; one of her two sons, Leo Wilhelmi, handsome with a mane of dark hair, handles day-to-day operations. At 66, she has a gamine energy and a feline intelligence, and could easily pass for a decade younger. Doubtless, she’d attribute her youthful glow to her decades-long adherence to fasting, both daily (in 16-hour windows) and twice yearly, when she follows the clinic’s regimen for 10 days or more at a stretch.
She invites me over for tea—fresh herbs, thyme picked from her garden—so she can explain the work here in person. Like the clinic’s staff and entire operation, the Swiss-born Toledo slides fluently between French, English and German as she talks; she has an evangelist’s charisma. Think of fasting as metabolic training, she urges, teaching the body how to use different energy sources, much as a hybrid auto switches between electricity and gas for efficiency. Hunger isn’t to be avoided but rather deployed, a forgotten reflex that we need to relearn. Toledo is pleased that the clientele here includes so many men as well as women—that 50:50 ratio is a rarity for conventional spas. “Fasting is not easy, as we take away everything you like at the beginning, so it’s more of a challenge. Men like that,” she says.
Indeed, it was a man who founded the clinic, a hundred years ago. His reasons were personal: Otto Buchinger, a physician, was wheelchair-bound from severe rheumatoid arthritis, at least until he fasted for almost three weeks on the suggestion of another doctor. Buchinger followed the most extreme protocols, ingesting only water. As a result, he later claimed, he was able to walk again. Buchinger turned his belief in the healing power of calorie restriction into his life’s work, setting up this clinic, which his descendants, including his great-grandson Leo, still run. But it is only in the last two decades or so that conventional science has turned its attention to the potentials of calorie restriction, and men have increasingly embraced fasting as the final fitness tool—a way to put their insides through as punishing a training regimen as they follow at the gym. Broadly speaking, there are two common approaches that aim to leverage reduced food intake for health and weight benefits. The first, periodic fasting, is the approach followed by the clinic; cut calories for an extended period every year or so, for example. The second is intermittent fasting, which deprives the body of nutrition in a given pattern each day or week: 16 consecutive hours in every 24 is popular (often called 16:8). Proponents claim both systems allow the body to shift into that sought-after state of ketosis.
Peter Bowes is a longtime BBC journalist who periodically fasts in his role as host of the podcast Live Long and Master Aging. During fasting, he says, the body undergoes autophagy, or spring-cleaning mode, meaning it recycles damaged or old cell machinery. Studies suggest that this process—which derives from Greek words meaning “self” and “to eat”—can even result in new synapses forming in the brain. “When your immune system is challenged like this, it throws out the cells it’s not using, that are maybe a little weather-worn,” Bowes says, “and builds a new immune system, re-growing white blood cells.”
A prolonged state of autophagy, then, could be thought of as a real-life counterpart to the serum that transformed scrawny Steve Rogers into super-soldier Captain America. Indeed, the US government has explored how to use intermittent fasting to improve the performance of elite commandos, according to Mark Mattson, a world-renowned expert in fasting and adjunct professor of neuroscience at Johns Hopkins University School of Medicine. Mattson says officials from NASA and the air force contacted him to discuss how to use his research in just this way. “It’s evolution,” he says. “If you’re food-deprived, you need to be more alert and motivated to find food—that’s why you often feel sleepy after a meal.” He suggested using intermittent fasting as a training tool, spending two days per week, for example, drinking only water. Mattson has focused his studies on such intermittent fasts and has a hunch it’s more effective than the Buchinger Wilhelmi method of one long annual fast, though he recognizes the benefits of calorie-deprivation of any kind. His research includes clinical studies of individuals at risk of cognitive impairment from Alzheimer’s and similar diseases, in which he found that those on a diet that included fasting showed memory and learning improvements within two months. Mattson says intermittent fasting is also a promising component in cancer treatment. “You should hit them in the fasting state with drugs or radiation because cancer cells cannot use ketones [as fuel], so if the glucose levels in the body are relatively low, it makes them more vulnerable,” he explains.
Andrew Jenkinson, a London bariatric surgeon and author of Why We Eat (Too Much), does not recommend long-term fasting but is a proponent of the 16:8 approach. “Ketogenesis is probably the best way to lose weight, but unfortunately, it’s difficult to sustain. Whatever diet you do for weight loss needs to be your new life,” says Jenkinson, who recommends a low-carb diet. “Fasting for a sustained period of time will improve the inflammatory response over the short term, and it will make you think faster and more clearly—it will give you a real buzz.”
Experts differ on how long it takes for autophagy to kick in from intermittent fasting—from right away to 12 weeks—but for optimal results, Toledo recommends practicing it five days a week. Jenkinson urges caution, too: Individual metabolisms and default weights vary. Veer from the program and you’ll likely rebound to where you started, he says. Though Toledo has led extensive in situ studies to determine the safety of the protocols used at the clinic, there are no records on the long-term efficacy of stays. The high ratio of repeat visitors could suggest that it is, indeed, hard to maintain such weight loss. Then again, it could be evidence of how effective her evangelical zeal proves in recruiting converts.
I’m impressed, if not completely converted, by day 10. At my final morning check-in with the nurse, I’ve lost close to 12 pounds and two inches from my waistline. More than anything, though, the stay here has changed the way I eat. I couldn’t even finish the first meal of solids, post-fast, served up with a candle and certificate in celebration. I’m just not as hungry as often anymore, and I’ve adopted that 16:8 system most days. Three months later, even during lockdown with limited exercise, I’ve remained slim. Would I come again? Absolutely. But perhaps the bigger question is: Why should I need to? Check back with me in a year.