It was supposed to be a spiritual experience.

Instead, I felt like a bottle of beer left out overnight, and if friends were to be believed, I also smelled like one. I could taste my own breath so intensely it formed a pressure system in my throat—a miasma huddling against my tonsils.

This shouldn't be surprising. For the seven days leading up to Christmas Eve, I subsisted on nothing but beer.

You are unlikely to find this diet recommended in the pages of Men's Fitness, but there are nonetheless those who believe in it. It is propagated mostly on the sort of online beer forums where stout men debate the merits of pancake-flavored porter. Inspired in part by the 16th-century Paulaner monks of Bavaria, who legendarily fasted during Lent by drinking nothing but doppelbock they brewed themselves, the diet enjoys a current small vogue that traces itself to a devoutly Christian Iowa man named Jay Wilson.

In 2011, Wilson decided to follow in the monks' footsteps, spending the 46 days before Easter drinking nothing but doppelbocks brewed specially for him at his local Rock Bottom Brewery. "I felt hunger for the first two days," he wrote in a CNN blog documenting his experience. "My body then switched gears, replaced hunger with focus, and I found myself operating in a tunnel of clarity unlike anything I'd ever experienced."

Wilson claimed his purpose was entirely religious, though he also reported a loss of 25 pounds.

Other beer bloggers followed suit with fewer religious scruples. These included Troy Rogers of Duluth, Minn., who in 2015 claimed a loss of 50 pounds in three months while on his own beer fast. "I love good beer," he told beer site the Growler. "I thought to myself, 'What if I do the opposite of what they tell you to do—I give up food and just drink beer?'"

It all seems too good to be true: weight loss and irresponsible indulgence together. Like CrossFit and juice cleanses, it is an affront to all moderation, less good health or discipline than a taunting dare to the human body.

And like all good dares, it was impossible for me to resist.

The first day, nonetheless, was terrifying. Food for me is a primary pleasure; a good meal is something I look forward to days in advance. Its absence threw my body's internal reward system into something approaching panic.

The primary quality of a beer diet, it turns out, is not drunkenness but hunger. It is less indulgence than an elementary math problem: How can you ingest enough substantive calories to live on, without also drinking yourself into sickness or debility?

The ancient monks most likely drank beer made with inefficient yeast, resulting in a low-alcohol brew thickened with unfermented, malty wort. Nothing like those beers exists today, when doppelbocks top 9 percent alcohol. And so I was left seeking a holy grail of high gravity, high calories and low alcohol.

During the first day of my beer diet, a Sunday, I failed badly at this. I drank saison and sour beer from my home fridge before finally going out for a pint of higher-calorie milk stout. In all, I ingested maybe 900 calories, and was famished. I slept terribly, and on Monday morning, I was human garbage. If colleagues questioned even the smallest thing I did, my response was to question the relative merits of their entire human existence.

"Wouldn't you like to work from home this week?" my editor asked, somewhat hopefully.

"If I suffer," I responded, "you suffer."

The best solution, it turned out, was dessert stouts: chocolate stouts and peanut butter stouts and stouts made with unfermented milk sugar. Nutella stouts, even (see page 28). They are the opposite of anything I have ever wanted from beer, novelty brews for drinkers with the palates of children. But they also act as the sticky-mouthed beer equivalent of a dietary supplement, though in this case the supplement is not nutrients but simple sugars—an adult candy diet for the pre-diabetic.

(Alyssa Walker)
(Alyssa Walker)
(Alyssa Walker)
(Alyssa Walker)

All week, I lived mostly on 22-ounce bottles of Samuel Smith chocolate stout. At only 5 percent alcohol, each bottle contains a whopping 400 calories and 4 grams of protein, otherwise in short supply in beer. It is delicious, in the way a chocolate protein shake can be delicious. And by chance it was on sale at New Seasons, reduced to $4.50 a bottle.

The idea was to space out the beers by at least three hours over the course of the daytime so I was never more than a little impaired. With three Sam Smiths I could be assured of 1,200 calories, leaving me free to drink whatever beer I wanted after work as a treat.

It was a perfect system, I thought—until at home, late Monday night, I broke down. I joylessly rammed a handful of stale, leftover Doritos into my mouth. Relief and guilt commingled, a sensation familiar to anyone raised Catholic.

I am a terrible, terrible monk.

Still, by Wednesday, I achieved a rhythm of sorts. I also came to accept low throbbing hunger as my lot in life. When other people ate doughnuts or hamburgers, I felt what house pets feel at dinner.

What devout Wilson said about achieving spiritual clarity was, of course, a lie: I merely grew accustomed to being a lower-functioning human being. On Thursday, I could feel my synapses refusing to fire, and in a fit of inspiration, I poured salt onto my palm and licked it like a tired horse, in an effort to restore neurotransmitter function. Strangely, it worked. I incorporated a daily salt lick into my routine.

By Friday, I noticed a strange, rotten-apple miasma lingering in my throat, and worried it was a sign of ketoacidosis—a diabetic condition that can be induced by a combination of alcohol and malnutrition. The owner of the paper left me an angry email complaining that my beer bottles were attracting flies. Also, I realized I hadn't had a bowel movement in three days. When it came, it was like squeezing oil paint out of a tube. I spent the next hour on the internet researching the Bristol stool scale, used to diagnose health from the consistency of your poop. It turned out there was no classification for what had just happened to me.

I was, I became keenly aware, unhealthy.

And yet by the time Sunday came, eating felt less like relief than chore. My stomach had shrunk enough that eating was a slog—and a lunchtime pizza felt like foreign, somewhat disgusting excess. Self-abnegation is apparently self-perpetuating; I had a sudden and shallow understanding of the revulsion that ascetics often feel toward food.

Aside from dropping half a belt loop, the main effect of my beer fast had been a renewed consciousness of just how compulsive most of my eating is—that I eat lunch because it is lunchtime whether or not I'm truly hungry, and that a large portion of my calories amount to a sort of primeval itch-scratching. I may even continue with some form of intermittent, beer-free fast—whether limited to specific times a day, or specific days a week.

But only one resolution is guaranteed. I hope to go the rest of the year without ever hearing the words "chocolate stout."