A fortnight with Silicon Valley’s fuel du jour. Could it make our writer faster, smarter, and more productive?

Coffee. Butter. Oil.

Separately those ingredients don’t exactly tick all the traditional boxes for a balanced breakfast. But together they are the three components you need to make Bulletproof coffee, a frothy, energy-igniting beverage that has surged in recent years to become the toast of Silicon Valley. Its promises are multitude, at least according to its creator, cloud-computing pioneer and "Bulletproof Executive" Dave Asprey, who refined his recipe after trying a tea made with yak-butter in Nepal.

Among Bulletproof coffee’s listed benefits: It triggers weight loss by way of ketosis, a metabolic state triggered by a lack of carbs that kicks fat-burning into overdrive; it kills pesky cravings; and it boosts cognitive function, mainlining a shining dose of mental clarity into your foggy morning skull. Maybe it would even fold my laundry.

Related: I’m The Guy Who Created Bulletproof Coffee—This Is My Morning Routine

Most of all, though, Bulletproof coffee is intended to be efficient, an easy way for the biohacking crowd to slurp down fats and calories (460 of them!) without so much as sniffing a processed carbohydrate. Why eat a muffin that goes straight to your muffin top, the thinking goes, when you could drink down the metabolic equivalent of supercharged battery acid every morning?

I was curious. I wondered: Is Bulletproof coffee a hyper-efficient, power-packed breakfast taken to its logical end? Or is butter-coffee something more insidious, the latest in a long line of snake oils intended to charm overwhelmed customers looking for the next big diet shortcut?

To find out, I recently gave up breakfast for two weeks and decided to dive headfirst into the (dark, mysterious, hot) Bulletproof hoopla. My goal was to assess a few things: How did I feel by lunch time every day? Did I feel notably sharper at work in the morning? And was brewing a cup of Bulletproof coffee anymore convenient than, say, pouring myself a bowl of cereal? Who knows: maybe I’d even drop a few pounds.

I began by ordering the starter kit from BulletProofExec.com, which has dozens of Bulletproof-branded products listed. The $38 kit includes:

1. Upgraded Coffee, which Asprey says is free of harmful mycotoxins, which are essentially fungi and mold, thanks to his top-secret roasting process. (More on this in just a bit.)

2. Brain Octane Oil, a supercharged version of MCT (Medium-chain triglyceride) oil. It’s supposed to be kind of like coconut oil, but it "works directly in cells to give you an extra boost to maximize your performance." (Whatever that means.)

Finally, I went over to Whole Foods in search of butter. But not just any spread would do! It had to come, per BPC’s recommendations, from the milk of grass-fed cows. I ended up going with a $7 pack of Organic Valley.

I guess now would be a good time to reveal my eating habits: I usually take my coffee black. I used to adhere to the paleo lifestyle, and later PDH, but now I eat anything. That is to say, mostly garbage. Luckily I still have the metabolism of a fresh-faced twenty-something. I’m not a gym rat like I used to be, but I do play basketball a few times every week, which is just about the only thing that keeps me in shape.

There, glad that’s covered.

Now, here is a vastly oversimplified and unscientific diary of what I learned from drinking Bulletproof coffee for two weeks.

Most days I wake up at 6:30 and try to get into the office by 8:00. Today, though, I decided to wake up at 6:00 and brew my first cup of Bulletproof coffee at home. After grinding the beans and brewing the coffee in a Chemex, I eyeballed a tablespoon of butter and a splash of MCT oil, figuring I would work my way up to the recommended two tablespoons of butter and tablespoon of oil from there. I opted not to blend it together–as BulletProofExec.com recommends–figuring I’d be making coffee at the office most of the time and didn’t want to cause a ruckus.

I squinted into my cup. The result was something that resembled an oil slick, with a yellowish sheen glazed on top of a dark murk. I gave it a few stirs and took a sip. It tasted wonderful. Butter tends to do that. It was thick, warm, and fatty, kind of like a Tonkotsu broth. The mysterious alchemy slid effortlessly down my tongue and esophagus, lubricating my throat and insides. I felt awake by 6:45.

On my commute into the office I felt more alert than usual–though it may well have been a placebo effect. Reading the morning news was a breeze, and I was burning through my Instapaper queue.

But by the time I arrived at work, I was already hungry; by 10 I was famished. When it came time for my 1 p.m. lunch meeting at a fancy Midtown gastropub, I wolfed down what should have been a decadent burger, barely even tasting it. I spent the rest of the afternoon gazing into my screen, debilitated with a severe case of the itis.

I decided to try and make Bulletproof coffee in the Fast Company kitchen with a Hario hand-grinder and an Aeropress. And I upped the butter and MCT oil to the recommended levels of two tablespoons and one tablespoon, respectively. Have you ever used a hand-grinder? Grinding enough beans for a single cup is a workout in itself.

Taste-wise the BPC was fine (less bitter, actually). And I was somewhat surprised by how quickly I’d gotten used to Bulletproof coffee’s broth-like consistency. I felt sharp as a tack. But by the time 10:30 rolled around I was hungry again, and had to fight with all the willpower I could summon to not take lunch before 11:00. Basically I was this guy.

 Days 3 and 4

Work was fine. I didn’t feel my usual morning grogginess. But feeling hungry by 10:30 was beginning to pose a problem. On the fourth day I had a tiny stomach ache from what I suspect was the coffee’s acidity.

I decided to email Asprey–or at least the press address listed on his website–to ask for advice on how to optimize my Bulletproof experience and perhaps do away with the stomach pains in the process. While waiting for an answer, I browsed through forums and came across what seemed to be one of the more popular solutions for dealing with hunger pains among the BPC crowd: throw a raw egg in it. Here’s what Asprey recommended in the forums:

I’ve done it with eggs quite a few times. The issue is that if the coffee is really hot it will oxidize the cholesterol in the yolks. You’re whipping it with air when you blend it…oxygen + heat. But if the coffee is just really warm it won’t be a big issue. Then if you want protein, it’s fine, but I find that adding protein to the morning fat meal will definitely end the Bulletproof Intermittent fast, so you lose the autophagy benefits. So for protein breakfast days, go for it, but not every day!

I couldn’t muster the courage to put an egg in my coffee; as one poster mentioned, wouldn’t dropping an uncooked egg into hot coffee result in egg-drop soup?

But protein? That I could do.

It was a Saturday so I slept in. When I woke up I did the least Bulletproofy thing possible: I ate a piece of toast. The goal was to give the coffee and its acid a spongey cushion, so as to avoid the stomach ache from the day before. At the advice of one of the forums, I also slightly decreased the amount of MCT oil.

And I can’t lie: After eating toast and slowly drinking down a cup of coffee, I felt great–the best I’d felt yet. Alert, strong, ready for life.

I had a basketball game at 9 a.m., for which I was running late. I brewed a weak cup of coffee, added in a sloppy spoonful of butter and coconut oil (hey, I was in a rush?) and chugged it all down. On the way to the game my stomach grumbled.

So I cheated. I ate a hoighty-toighty artisanal donut made with hibiscus flowers. Things got a little weird: Sugar in the morning tasted goddamn amazing. I suddenly felt amazing. Everything was amazing. I had tons of energy during the game. Was my body trying to tell me something?!

And the game? We lost.

Monday. I decided to wake up early again and brew the coffee at home. I thought: Maybe the deliberateness of the brew method would trick me into feeling fuller longer, like the act of cooking dinner before eating it, or chewing something 24 times before swallowing.

Didn’t work. I was hungry by the time my commute was over. Emerging out of the subway station, I passed by a bakery and caught a whiff of croissants. Flakey, buttery, carb-loaded croissants. I lowered my head and fast-walked to work.

I needed help. I asked Asprey on Twitter if he’d be open to chat. He told me to email him (for the second time), so I did.

No response.

I had a bit of extra coffee in the Chemex from the day prior, so I microwaved it, dumped it into a to-go cup, threw in a few spoonfuls of butter and MCT oil, and shook the thing like a maraca. Drinking butter-coffee on public transit is strange. I felt like my lips were extra shiny, as if I were wearing lipgloss.

When I got into work, though, I somehow found myself with a gnarly stomach ache. And–surprise, surprise–I was ravenous. At around 11, when a company-wide email pinged my inbox and said there were free bagels on the snack table, I was the first one to zip out of my seat, pouncing on the table like a lion stumbling upon a fresh zebra carcass. My zebra had poppy seeds.

I felt guilty. This "experiment" was going south. Fast. One thing was clear: Something essential had to change.

On the way home that night I bought some organic whey protein. A friend recommended I try switching to Kerrygold grass-fed butter, so I bought a stick of that, too.

Before going into the office, I first stirred a scoop of whey protein into a glass of water and guzzled it down. At work, I made a perfect little cup of Aeropress coffee with two tablespoons of Kerrygold butter, along with the full recommended amount of oil.

And guess what? I felt fantastic. I’d reached a new plateau: My stomach didn’t hurt. I wasn’t super-hungry by noon. My writing-brain was firing on all cylinders, effortlessly bending metaphors and contorting sentences to do whatever I wanted. I felt a sustained burst of energy that felt as if it might never taper off. It was as if I had hit the gym hard that morning, and then dumped a bucket of ice over my head.

Had I finally unlocked the secret formula?

I was ‘effing crushing it at work, bro! Hundreds of not-awful words were being transposed perfectly from my brain, through my fingertips, and organically arranging themselves into phrases on the Internet. At that point I was all in on the Bulletproof express, and it was trickling into other aspects of my diet. I was drinking less beer, eating less carbs, and feeling better overall.

One night, I looked at myself in the bathroom mirror. Holy hell. Is that an ab? It wasn’t. But I sure felt like a million bucks.

Asprey still hadn’t responded to my emails, so I decided to ask how other people acclimated to drinking BPC.

"I’ve been drinking it for the better part of two years now," says Jeff Ake, a personal trainer and fitness coach based in Denver, Colorado. "I don’t drink it every day. But I was waking up, putting things like grains and simple carbs in my stomach in the morning, and I would burn through those really, really quickly."

Ake says before BPC he felt lousy. Drinking it was a revelation: It kept him full for five to six hours at a time and gave him a bundle of energy, allowing him to stay on the training floor with clients for long and demanding stretches. He preferred his BPC with Stevia, coconut oil (instead of MCT oil), and a little bit of vanilla extract. I made a note to try it.

Then I asked Ake: "Do you remember how you first heard about Bulletproof coffee?"

"I heard about it through whatever his name is," he said, referring to Asprey. "He was on the Joe Rogan podcast probably two years ago."

Once we were done chatting, I Googled "Joe Rogan" and "Bulletproof coffee." This was one of the first search results:

Watch it. Rogan is livid.

I fell down a rabbit hole. Apparently Asprey had appeared on Rogan’s podcast a few days prior, expounding on Bulletproof’s many miracles. Ever the charmer, Asprey had converted a wide-eyed Rogan to the Church of Grass-Fed Butter, and Rogan would go on to sing BPC’s praises anywhere he had a pulpit.

The singing didn’t last long, though. Rogan soon discovered that one of Asprey’s key claims–that 70% of all coffee beans were laced in vitality-sapping mycotoxins, which he claimed also makes coffee bitter–turned out to be false.

"Good coffee providers know how to eliminate this from coffee," Rogan said on his show, citing a study he found on PubMed from the 1980s. "They’ve been able to solve it [for decades] with something called wet processing." When the coffee plant’s berries are picked, the cherry (or bean) is "washed" in running water before it’s left to ferment and dry, reducing mycotoxin levels to negligible amounts. Everyone from Stumptown to Starbucks washes their beans this way.

That’s why Rogan was pissed. He felt betrayed, and accused Asprey of spouting pseudoscience veiled as fact. "There’s some bullshit there, for sure," he said. "He used my platform in a way that’s non-ethical."

It was the weekend. Since I had time in the morning, I made BPC the way it was intended: Slowly, using a pour-over, with all the ingredients dumped into a blender. The resulting sludge was thick, like a milkshake. Drinking BPC this way did have one surprising side-effect: The fridge-cold butter made the normally hot coffee lukewarm, barely above room temperature.

I still had plenty of energy. But I missed eating solid food in the morning.

Figuring my two weeks drinking attempting BPC were basically up, I caved and decided to celebrate that morning in the form of a breakfast sandwich–an egg and cheese on a croissant from that bakery. In a cosmic fit of groggy clumsiness, the croissant exploded like a flakey piñata, sprinkling crumbs all over my keyboard.

An hour or so later I felt noticeably sluggish; my brain was a step behind, like its cogs were bogged down by the drink.

So at around 10, I went to the office kitchen to make a cup of BPC. When I opened up the fridge, my fancy-schmancy Kerrygold butter wasn’t there. I leaned into the fridge, looking behind every sad tupperware.

Someone had either thrown it out or taken it home.

My feelings about BPC are mixed. On the one hand, it gave me lots of energy (even if I should get my cholesterol checked). On the other, like an increasingly vocal group of critics, I’m wary of the claims that Asprey–a very smart guy who is obviously onto something with his Bulletproof empire–uses to market it.

"I would most certainly not recommend it," says Christopher Ochner, a nutrition expert at the Icahn School of Medicine at Mount Sinai Hospital. "Now there is a little bit of data on the use of medium-chain triglycerides for weight loss and regulating cholesterol. But the effect is very, very small."

A few days after the experiment concluded, I asked Dr. Ochner why I was still hungry after drinking down hundreds of calories worth of saturated fat every morning. "Well, that’s not actually surprising," he says. "The people making these claims know there’s a lot of evidence that drinks and shakes don’t really make people feel full. Even if you drink a big Coke with your meal or whatever, and that could be 400 calories or more, it doesn’t really make a huge dent in people’s appetite. It’s the same concept."

All told I probably wouldn’t cough up $40 again for the special mycotoxin-free beans (the process of which Asprey won’t share publicly) or MCT oil. I’d probably stick with non-Bulletproof-branded ingredients.

Brewing BPC every morning wasn’t very convenient either. As a meal replacement, drinking down whey protein and then making a steaming cup of BPC was more work than it’d take to say, scramble a few eggs. (In fact, brewing coffee this way gave me more dishes to wash.)

Unless I dramatically overhauled my diet and lifestyle–and I’m keenly aware that I didn’t during my Bulletproof fortnight–I don’t think strictly adhering to the butter and oil approach would make anyone feel invincible, or noticeably healthier. The good news is that at BulletProofExec.com–on the same page as the Bulletproof T-shirts ($20), travel mugs ($30), and anti-aging skin creams ($99)–there is a Bulletproof Diet Roadmap poster ($9) that shows you how to perform just such an overhaul.

I’ll still drink a cup of Bulletproof coffee from time to time. But the truth is, I’d much rather eat breakfast.

About the author

Chris is a staff writer at Fast Company, where he covers business and tech. He has also written for The Week, TIME, Men's Journal, The Atlantic, and more. More