I tried the popular Silicon Valley diet credited with boosting energy and prolonging life -- and I can see why people are obsessed

Erin Brodwin / Business Insider

I’ve been ignoring my mother for a week and a half.

For the past 10 days, I’ve stifled the small voice she instilled in the back of my mind to remind me that forgoing breakfast is nutritional doom – all for the sake of a diet known as intermittent fasting.

The diet essentially involves abstaining from food for a set period of time ranging from 16 hours to several days – and surprisingly, it has a lot of scientific backing.

Large studies have found intermittent fasting to be just as reliable for weight loss as traditional diets. And a few studies in animals have suggested it could have other benefits, such as reducing the risk for certain cancers and even prolonging life.

Silicon Valley loves it. A Bay Area group called WeFast meets weekly to collectively break their fasts with a hearty morning meal. The Facebook executive Dan Zigmond confines his eating to a narrow time slot; many other CEOs and tech pioneers are sworn “IF” devotees – some even fast for up to 36 hours at a time.

I opted to try a form of the diet known as the 16:8, in which you fast for 16 hours and eat (or “feed,” as some proponents call it) for eight hours. With this regimen, you can eat whatever you want – as long as it doesn’t fall outside the designated eight-hour window.

Here’s how it went.


Before starting my fast, I checked in with the doctor Krista Varady, one of the first researchers to study intermittent fasting in humans. I also had a standard checkup with my primary-care doctor.

University of Illinois at Chicago

Varady is a nutrition professor at the University of Illinois and wrote a book about fasting called “The Every-Other-Day Diet” in 2013. She told me the most scientifically supported benefit of intermittent fasting was weight loss.

Most of Varady’s IF research has involved obese people. Study subjects have lost a significant amount of weight – roughly the same amount they would have on a traditional diet that involves strict eating and calorie counting.

I told Varady I was trying out the diet not to lose weight but rather to find out how feasible the plan was. She said that while certain people shouldn’t try intermittent fasting – those over 70, people with Type 1 diabetes, and women who are pregnant or lactating – “most people can give it a try.”


Some research suggests that intermittent fasting has a handful of other benefits, from increased focus to a reduced risk of certain diseases. Some studies even suggest it may help prolong life, but most of that research has been in animals, not people.

Melia Robinson

Anecdotally, intermittent fasters report that their diets have helped them become more productive, build muscle faster, and sleep better. Members of a Silicon Valley startup called HVMN skip eating on Tuesdays and claim they get more work done on that day than any other.

Varady said hundreds of people in her studies had reported similar benefits. “But we haven’t studied or quantified any of that yet,” she said.


With the go-ahead from my doctor and Varady, I was ready to find out for myself. Based on advice from other IF fans, I chose to break my daily fast at noon and stop eating at 8 p.m., giving me eight hours to eat or “feed.”

I wanted the last meal before my first 16-hour fast to be good, so I made one of my favourites: homemade pizza with arugula and chicken breast.


My first day of fasting began with an iced coffee. Intermittent fasters are allowed to drink fluids including tea and coffee during the fast, but no sugar or cream is allowed.

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Then I headed to a morning yoga class. I have to admit feeling a little trepidatious about exercising without my typical morning fuel.


My workout went better than I expected. The hunger pangs I felt during the warmup quickly faded. During class, I felt more energised than usual. At work afterward, I didn’t start to feel peckish until 10 a.m., so I poured myself another black coffee.

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The coffee helped curb the cravings for a while, but I started to feel ravenous at about 11 a.m. At 11:45, I set a timer on my phone for 15 minutes.


Finally, it was noon. I ate the lunch I’d prepared: a salad of spinach, chicken breast, cheese, and a banana for dessert. I savoured the sweet taste of victory: My first 16-hour fast was over. But I wasn’t prepared for what happened next.

Erin Brodwin / Business Insider

About 30 minutes after inhaling my meal, I started to feel dazed. I had trouble focusing. My hands and fingers, which are normally a bit cold, felt like ice. I wasn’t hungry, but I suddenly felt as if I hadn’t eaten in days. On a tip from a practiced intermittent faster, I went for a long walk.

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About 20 minutes into my walk, I began to feel slightly better, but I still couldn’t really focus. When I got back to the office, I managed to get a few things done but still didn’t feel like myself.


Later that day, the fog faded and I felt normal again. Soon after that I found myself ploughing through work with more energy than usual. Around dinner time, I noticed another change — I didn’t feel as ravenous as I usually do. So I warmed up a couple of pieces of leftover pizza and skipped my usual dessert.

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The next day, I woke up determined not to be thwarted by the previous episode of brain fog. For lunch, instead of a container full of lettuce and a bit of chicken, I had a hearty bowl featuring loads of grilled chicken, half an avocado, cheese, veggies, and black beans.

Erin Brodwin / Business Insider

After lunch, I felt great. I was focused, full, and ready for an afternoon of work.


That evening, however, I encountered my first challenge: dinner with friends.

Luckily, the friends who invited me over wanted to eat at about 7, well within my “feeding window.” We planned to order takeout, but, unfortunately, some of us arrived late. By the time we ordered, it was 8 p.m., and the food didn’t arrive until 8:30 (after I was supposed to stop eating for the day).

It felt weird to refrain from eating with everyone, so I decided that the next day I would break my fast an hour later to make up for it.


But delaying my break-fast was a mistake. By 10:30, my stomach was growling. I couldn’t think about anything other than food. I kept drinking coffee and water, hoping I could quell my appetite with liquids and caffeine.

Erin Brodwin / Business Insider

By 11:45 a.m., I was ravenous and shaking from all the coffee. I decided to eat at noon again despite the promise I’d made the night before. The rest of the day went all right, and for dinner I heated up a frozen meal from Trader Joe’s.


The next day I faced my second challenge: travelling while fasting. My office had an overnight work retreat planned, and everyone was ready to pile in the car around noon — the exact time I was supposed to break my fast.

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In a rush, I grabbed a Clif bar, a handful of almonds, and some seaweed snacks from my desk. I scarfed it all down as we drove.


When we arrived, we went for a hike in California’s Año Nuevo state park. It was gorgeous and I was feeling energised and happy — despite the fact that I’d also worked out in the morning and had hardly eaten.

Melia Robinson / Business Insider

Some of the intermittent fasters I spoke with told me they preferred to work out in the middle of their fast since exercising in that state gave them more energy during heavy bouts of training.

The science doesn’t necessarily support this, however. In one large recent study, scientists reviewed several studies of Muslim athletes. They had been practicing one of the oldest forms of intermittent fasting – abstaining from food and drink from sunrise to sunset during the holy month of Ramadan.

The reviewers found that as long as the athletes ate the same number of calories and nutrients when they broke their fasts, their athletic performance didn’t suffer or improve during Ramadan.


After the hike, my coworkers and I met up for dinner at a taco joint. When we arrived, I was famished. Instead of being polite, I marched to the front of the line and was first to order.

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I got two chicken tacos, chips and salsa, and a side of refried beans.

When I took a bite, the flavour of the grilled chicken seemed to dance on my taste buds. The corn tortillas were soft, light, and delicious. The beans were hearty and had a kick of spiciness that I loved.

I realised I was tasting the food more intensely than usual – as if my senses were heightened. Perhaps narrowing my eating to a specific window of time made me pay more attention to my food. It seemed to make the act of eating more enjoyable, too.


After the meal, I was stuffed. My coworkers decided to make s’mores, but by then it was 9:30 p.m. — well past my eating time. I didn’t want to miss out, so I headed over to the campfire and helped other people roast their ‘mallows.

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That night, I went to bed feeling great about my self-control. When I arrived at the conference center my office had booked for our retreat, however, I couldn’t help staring at the breakfast spread.

There was fresh fruit, yogurt, and a plate of whole-grain muffins that looked as if they’d been baked that morning. I was tempted but moved on.

Around 11, I was hungry and decided I’d earned a small cheat, so I added almond milk to my second cup of coffee. It tasted sweet, nutty, and wholesome – and after skipping out on s’mores, I didn’t feel guilty.


The day before, I’d made a mistake in assuming that I’d be able to eat lunch right at noon. This time, I prepared by saving some nuts as an emergency snack.

That turned out to be a good idea. My meetings ran well past noon, but I was able to break my fast with a hearty snack. When lunch arrived, I was still hungry and ate a blackened-salmon burger with salad and some berries. I felt as if I could have kept eating for hours but tried to control myself.


After lunch, someone broke out the rest of the s’mores supplies, and this time I could enjoy the treats.

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After a couple of raw s’mores, I was feeling a little giddy from all the sugar.


When I got home after my office retreat, I wasn’t super hungry but didn’t want to miss my window for dinner. So I made some scrambled eggs and smoked salmon on toast.

Erin Brodwin / Business Insider

The next day, I hit the gym in the morning with more energy than usual. I powered through about twice the miles I normally do on the stationary bike, then ran a few errands. I broke my fast at noon with a small plain yogurt, but then oddly forgot to eat for the rest of the day. I had a few bites of chicken breast and veggies at about 5 but wasn’t hungry. It was a mistake I’d pay for later.

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My lack of appetite is one of the reasons I think people would be drawn to intermittent fasting. Though the idea of a “fast” – which implies denying yourself food – sounds tough, I did occasionally experience less hunger overall when I did eat.


The next day started out well. I had pizza, my first meal of the day, around 12:15 p.m. But afterward I had a strong and unusual craving for something sweet, so I stopped by a newly opened bakery.

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To celebrate the store’s opening, there were plates stacked high with free alfajores – delicious South American cookies sandwiched together with a layer of dulce de leche. I quickly polished off four alfajores, which I later calculated had more calories than one of my normal meals – and way more sugar and refined carbs than I would normally eat in a day. But hey – I didn’t break my diet!


That night after dinner, my sweet tooth had yet to be satiated. Around 11 p.m. — three hours past my eating window — I was overwhelmed by a craving-fuelled urge to make s’mores. Armed with the leftover supplies from my work retreat, I fired up the stove.

Erin Brodwin / Business Insider

By midnight, I’d eaten four s’mores and some vanilla ice cream, and felt as if I could keep going. Only my lack of supplies stopped me. I love sweets, but this was abnormal even for me. It was as if my stomach had no bottom. All I wanted was more chocolate.


The next day, I felt guilty and went back to my fasting routine. I skipped breakfast and broke my fast at noon with a healthy-but-hearty lunch: turkey breast, cabbage, spinach, a scoop of egg salad, and some hummus.

Erin Brodwin / Business Insider

Afterward, I felt much better than I had for the previous 24 hours. The problem with sweets (like the ones I’d gorged on) is that they’re high in refined carbs and sugar, neither of which fill you up or fuel your body long term.

My guess is that after I forgot to eat, my body went into starvation mode. Then, when I consumed heavy, rich treats, it went into overdrive and started craving more and more of them.


For the next two days, I ate healthy, filling meals. I made salads full of beans, chickpeas, and lean meats or eggs; whole-grain pasta with chicken breast; and vegetable stir-fry with brown rice and tofu. I also drank a ton of water — sometimes up to 15 glasses a day.

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Varady told me that not drinking enough water was a central pitfall of the diet. “Many people who try the diet complain of things like headaches. But the problem is a lot of them aren’t drinking enough water,” she said.

Roughly 20% of our daily fluid intake comes from food, so if you’re fasting, you may need to add a few glasses of water to your day.


Overall, I learned a lot about my body by trying intermittent fasting, but it was one of the hardest things I’ve done.

When I stick to a fairly healthy diet full of vegetables, whole grains, healthy fats (avocados and nuts), vegetables, and small amounts of lean meat and dairy, I feel good – no matter when I eat.

And when I eat like that, I can enjoy the occasional sweet treat – be it a s’more or an alfajor. But when I get too rigid with my eating by denying myself certain things, or when I forget to eat altogether, it puts me in a danger zone where I crave unhealthy foods that ultimately don’t nourish my body.


I don’t think intermittent fasting is the right eating plan for me, but I see how it could work wonders for some. It reduced my opportunities to snack, curbed my appetite (at least on the days when I followed it properly), and pushed me to focus on and enjoy my food when I did eat.

Erin Brodwin

Intermittent fasting also appeared to eliminate my late-night snacking habit and seemed to give me more energy throughout the day. I’m glad I gave it a shot, but for now, I’m back to three meals a day – plus the occasional sweet treat.

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