This Is What Happened When I Tried The Silicon Valley “Biohacking” Fasting Trend

Some Silicon Valley execs swear that a form of fasting they call “biohacking” makes them more productive. To find out if it really worked, I tried it myself.

This Is What Happened When I Tried The Silicon Valley “Biohacking” Fasting Trend
[Photo: Weedezign/iStock]

There is a small but growing trend among some Silicon Valley executives called “biohacking.” The term refers to extreme fasting not for the weight loss or health benefits, but for the productivity benefits.


Its proponents include Phil Libin, the former CEO of Evernote and current CEO of AI studio All Turtles; Y Combinator partner Daniel Gross; and Loic Le Meur, the cofounder of the LeWeb tech conference. Participants in biohacking swear off all foods for between two to eight days at a time followed by similar time lengths of time where they eat normally. During their fast periods, they’ll only consume liquids like coffee, tea, and water.

Related: The Fasting Fad Likely Isn’t Going Away Anytime Soon

As Libin told the Guardian: “There’s a mild euphoria. I’m in a much better mood, my focus is better, and there’s a constant supply of energy. I just feel a lot healthier. It’s helping me be a better CEO. Getting into fasting is definitely one of the top two or three most important things I’ve done in my life.”

Of course, these tech leaders didn’t invent the idea of fasting. It was undertaken for the supposed health benefits thousands of years ago by the ancient Greeks, and virtually every major religion includes periods of fasting for devout believers. Fasting has also been used as a political protest tool–aka the “hunger strike”–for centuries, perhaps most notably by Gandhi. And of course fasting has more recently been co-opted by the diet industry and its gurus–a recent example being the 5:2 diet.

As for the most recent iteration, proponents of the “biohacking” fasting diet theorize that the productivity benefits gained may be due to a rise in ketones in the body during the period. Ketones are produced when the body has insufficient calorie intake and thus starts burning fat for fuel. They say these ketones are “super-fuel” for the brain, which increases mental clarity and performance. I wanted to check their theory with someone knowledgeable about foods’  effect on the human body so I spoke with Rhiannon Lambert, a leading  nutritionist who has written multiple books  including the forthcoming Re-Nourish: A Simple Way to Eat Well.


“Clinical research studies of fasting with high levels of evidence are scarce,” she cautioned. “While the few randomized controlled trials and observational clinical outcomes studies support the existence of a health benefit from fasting, substantial further research in humans is needed before the use of fasting as a health [and productivity] intervention can be recommended.” That being said, she did say that there is some limited research that does show fasting can benefit the brain. “Intermittent fasting can see increases in a particular brain hormone called BDNF, which may aid the growth of new nerve cells.” She says that the research shows this new nerve cell growth suggests fasting may protect against Alzheimer’s disease.

But would giving up food for a few days really increase my productivity? I wanted to find out, which is why I decided to mimic the Silicon Valley execs’ “biohacking.” For 10 days I did intermittent fasting. For two days I would consume nothing but coffee, tea, or water followed by two days of eating normally and then repeat the process. Here’s what I experienced:

[Photo: ttatty/iStock]

 My Nutritionist:”I Do Not Recommend This Type Of Fasting.”

When I first ran my intermittent fasting routine by Lambert, I told her I was going to fast for three days and then eat for two, before repeating it. But her reply made me rethink my plan a bit.

“This fasting technique is extreme as it is fundamentally calorie restriction, which may lead to a variety of problems,” she warned me via email. “Eating fewer calories than your body requires can cause fatigue and make it more challenging for you to meet your daily nutrient needs.” Further, she said that if I were fasting for three days at a time, on the days I did eat my nutrition needs would need “to be planned meticulously.” And she wasn’t done. “Restricting calories may also disturb hormone levels, which may result in weaker bones. Bone loss is especially worrying because it is often irreversible and something that can creep up without symptoms until the damage has been made.”

Further, she had written, “I do not recommend this type of fasting as it creates a different mind-set around food.”


Still, I was really curious about the supposed productivity benefits so I decided to carry on, although with a slightly reduced fasting schedule (two days at a time instead of three). But I thought, really how hard could this be? I gave up sugar for two weeks before and survived, after all. At least with intermittent fasting, I could eat whatever I wanted on my “off” days.

Unsurprisingly, I Was Starving

When I woke on my first fast day I was in good spirits. By lunchtime I was golden. This was going to be a cakewalk. By dinner, I was pretty hungry, but still, what’s a little suffering? By breakfast time the next morning, I was absolutely starving. I must have had close to 10 cups of coffee and over 120 ounces of water in an attempt to satiate my hunger.  It  didn’t work,  by the afternoon I found it hard to concentrate on anything but my hunger and because of that, I found it hard to really dedicate myself to work. I still got my work done,  it just wasn’t any good. I definitely was not experiencing anything like Libin’s “mild euphoria:”  better mood, improved focus, or increased energy. In fact, it was quite the opposite. I was cranky and making silly mistakes. For example, I’d read an email or a Slack message from someone and realize moments later I hadn’t actually been paying attention to what I was reading so I needed to go back and reread it again–and again.

[Photo: tashka2000/iStock]

Once I Started Eating I Went Back To Normal

Ironically, when I woke on the third day (my first eating day) I had expected to run to my kitchen to eat as much as possible as fast as possible. Yet when I woke, my hunger was gone. Literally, it wasn’t there anymore. I felt as if I didn’t even need to eat. And I actually didn’t, not until I made myself a sandwich later in the day.

By that third day, I also noticed that I could concentrate just as well as I normally do. This familiar concentration was back with me in the morning when I worked before eating that sandwich, and it was definitely still with me after I ate my first meal for lunch in two and a half days. The slightly disappointing thing was that though my concentration was back, I didn’t notice any “productivity boost” the Silicon Valley execs report.

Maybe I would during my next two-day fasting cycle?


The Next Two Days Of Fasting Weren’t As Bad

After two days of eating regularly, I was dreading going back to two days of fasting. Though by the third day I was no longer starving, I remembered how bad that second day was. Surprisingly when I began my second set of two-day fasting I found myself nowhere near as hungry as I did during the first set.

Of course, the bad thing was that, by the end of that second two-day set, I had not gained any superhuman abilities to be more creative, reply to more emails, or otherwise noticed any other productivity benefits.

10 Days Of “Bio-Hacking” Did Nothing For My Productivity

Throughout the rest of my 10-day experiment, disappointingly, I didn’t notice any productivity gains. I had gotten used to the cycle of intermittent fasting and I no longer “starved” on fasting day–not to mention I did lose 10 pounds–but that was it.

Does that mean the Silicon Valley execs who do this type of “biohacking” are full of it? No. After all, they do intermittent fasting for much longer than I did. Plus they sometimes fast for as long as eight days at a time. Yes, their experiences are subjective–just as mine were–but perhaps the length of time they have intermittently fasted for are the differentiating factor. Of course, perhaps they just want to “see” benefits where none actually exist.

For me, I’ll stick to giving up sugar for the productivity benefits over intermittent fasting. At least I know that works.

About the author

Michael Grothaus is a novelist, journalist, and former screenwriter. His debut novel EPIPHANY JONES is out now from Orenda Books. You can read more about him at