“If there’s a downside, it is kind of crazy tasting,” said Geoff Woo, the founder of HVMN, a Silicon Valley company that makes nootropics, or performance-enhancing supplements. We were in a conference room in The Atlantic’s office building, and he was bracing me for my trial run of his latest product.

It was a small, clear vial labeled “Ketone,” a new type of energy drink his company is releasing this week. Its nutrition label says it contains 120 calories, but no carbs, no fat, and no protein. Instead, it’s all ketones, the chemical that Woo and his company are calling a “fourth food group.” He hopes the drink will allow people to reap the benefits of occasional fasting—high ketone levels inside the body—without actually having to not eat.

I unscrewed the top and, college-days muscle memory kicking in, chugged it like a shot of Captain Morgan. It tasted like cough syrup that had been poured into a garbage bag and left in the sun.

“Augh!” I cried.

“I compare it to a combination of a liquor shot with nail-polish remover,” Woo said.

Woo’s coworker, Brianna Stubbs, went to fetch me a glass of water. “We’ve done a lot of work to make it better,” she said.

Within an hour, the drink was supposed to help improve my athletic performance by changing how my body burned energy during exercise. Some people also say it helps them feel more energetic and focused on their work.

About 25 minutes after I drank Ketone, Woo and Stubbs pricked my finger to see if it was working. My blood sugar, which had verged on diabetic levels from some pineapple I had eaten that morning, was down to near-normal levels. Meanwhile, my ketones, which had been practically nonexistent before imbibing—measuring just 0.2 millimolar—had soared to 4.9.

“It would have taken me six days of fasting to get to that level normally,” Woo said. “To hit five is pretty crazy.”

* * *

Ketones are chemicals made from fat that the body burns for fuel when it runs out of carbohydrates. The process of burning these ketones is called “ketosis,” and it can be achieved through either fasting or through a “ketogenic” diet that’s high in fat and very low in carbohydrates. The ketogenic diet was initially developed more than a century ago to control seizures in epileptic children. Today, some healthy people fast intermittently or follow ketogenic diets in order to remain in a near-constant state of ketosis, saying it helps them control their weight, feel more energetic, and stay focused.

My trial bottle of Ketone (Olga Khazan / The Atlantic)

Woo says he fasts for at least 18 hours a day and runs an 8,000-person-strong intermittent fasting group. He subscribes to fledgling evidence showing that fasting might help boost neurogenesis, or the growth of new brain cells, as well as lead to longevity. When he met me at 11 a.m. in Washington last week, he only had coffee and seltzer that morning.

“I would say almost standard eating is an eating disorder, in the sense that when you get invited out for happy hour or a lunch meeting, we don’t do that because we’re hungry,” Woo said. “We do that because it’s a cultural norm ... Romans centered their meals around one large meal a day, typically around lunch. A lot of East Asian cultures had two large meals a day. ”

Though ketones are considered an especially efficient energy source, the liquid version isn’t found in food; it had to be manufactured in a lab. Because the keto diet can be unappealing—low on fruit and vegetables and high on bun-less burgers—it can be hard for all but the most committed to stick with it. And though intermittent fasting can help the body attain the same reported benefits, fasting is, well ... fasting.

Kieran Clarke, a professor of physiological biochemistry at the University of Oxford, began researching dietary ketones in 2003 as part of a U.S. Department of Defense grant that was intended to find ways to help troops perform better on the battlefield. She and her collaborators created the ketone ester, as these liquid ketones are called. Clarke founded a company, T∆S, to market her findings, and she licensed the intellectual property to HVMN (which is pronounced “human”).

Each bottle of HVMN’s Ketone provides 25 grams of the ketone ester. The drink can now be preordered, but it doesn’t come cheap: A three-bottle package—three doses meant to be taken, at most, within a day—sells for $99. The FDA has blessed HVMN as “generally recognized as safe,” but it’s considered a food, not a supplement.

You’re supposed to take the ketones an hour before you work out to boost performance, or 30 minutes after you exercise for recovery. The company claims that some people feel a sense of enhanced focus and “flow” after drinking the substance, though the evidence behind this claim is less established.

It’s not necessary to fast or follow a ketogenic diet while drinking Ketone, but Woo said it could be a type of “bridge” to get people through the first few rough days of fasting. (Clarke, in fact, recommended drinking Ketone with a banana or another carb, so the body has its choice of fuel.)

In a study of 39 elite cyclists published last year, Clarke and others found the athletes were able to go 400 meters further in half an hour after drinking a ketone drink, compared with a carbohydrate- or fat-based energy drink. One reason for the increased performance could be that their muscles contained lower levels of lactate, which causes an achy feeling while working out. Rats on a ketone diet have also run farther on a treadmill and completed a maze faster than rats on a regular diet.

Ketone esters have been shown to have some promise in Alzheimer’s patients and in people with traumatic brain injuries as well, but research on ketones’ cognitive benefits is still very early.

Most recently, Stubbs, a scientist with HVMN and a British rowing champion, found that ketone esters can suppress appetite by controlling ghrelin, a hunger hormone. The reason my glucose dropped after drinking Ketone, Woo speculated, is that the drink signaled to my liver to stop releasing sugar. He is hopeful that, eventually, dietary ketones could become a treatment for people with type 2 diabetes.

“If you can replace some of the calories in your diet that would have come from carbohydrate and refined sugar with ketones, now that it’s in a bottle ...” Stubbs said.

“This is so much grosser than a donut, though, I have to tell you guys,” I said.

“We’ll work on putting it in a donut,” she replied.

Several dietitians have tossed cold water on the idea of ketosis in a bottle. “I have not yet found one ketone-ester supplement that has been able to successfully put someone into the state of ketosis, no matter what dosage they take,” Ben Sit, the president of Evolved Sport and Nutrition, told BuzzFeed News.

Over email, John Newman, a professor at the University of California, San Francisco, said, “I’m a little skeptical about the idea of enhancing performance in young, healthy people—I’m a geriatrician after all. However, the older patients I care for in the hospital would certainly be better off if they could recapture some of the resilience that their brains and bodies had when they were younger.”

He said there’s still a “lot of hard work” remaining to determine if ketones can translate to better health.

* * *

I drank Ketone on two different days, and on one of them, I went for a run to test out the sports benefits. The thing is, I’m an abysmal runner. I recently ran a 5k and would have finished last in my age group, had there not been some people on actual crutches participating. On Ketone, I did manage to run about two-and-a-half miles in 30 minutes, which is actually good for me. But any dreams I had of finally lapping moms with jogging strollers were pretty much dashed.

For me, the clearer Ketone benefit was cognitive: I had the most incredible surge of positive energy I’ve had in months. I’ve never been one of those people who is happy for no reason, but I found myself smiling at strangers and cheerily making small talk in the office kitchen. Even more surprising is that the previous night, I had taken a red-eye flight and gotten almost no sleep.

On Ketone Day, I was able to stay working on a story late into the evening, and I barely noticed the extra hours roll by. And when I reread it, the story even made sense! This is the best drug ever! I thought. I am Ethan Hawke in Gattaca, not saving anything for the swim back. I am Jessie Spano, so excited and so scared. I can’t wait to get my hands on a case of these suckers!

Then I remembered something from the last big story I wrote about nootropics. In the absence of clear metrics on cognitive enhancers—how much more productive was I, really?—a placebo effect can sometimes take hold. “You can give people lemonade and tell them it’s a cognitive enhancer, and they’ll get perky,” is how Derek Lowe, a science blogger and expert on drug discovery, put it to me then.

Indeed, Clarke burst my bubble: “The ketones are all gone within three hours. There’s absolutely nothing left after three hours,” she said. In other words, it’s unlikely the ketones I drank at 11 a.m. could have been amping me up at 9 p.m.

When I visited San Francisco for my last story on nootropics, everyone I met seemed really ... on. Many of them ate special diets, or had “stacks” of pills and supplements they took to keep their focus heightened. Or at least, they believed it was heightened. But for hyperintelligent people looking for just a micron of an edge over the competition, there’s not much of a difference between the two.

I might glug some ketones if I ran marathons, or if I faced some grueling concentration task, like a paper to write in a hurry. But I wouldn’t expect this company’s beverage to magically transform you from a couch potato into an Olympian or hyper-focused work robot. They’re only HVMN, after all.