I tried the popular Silicon Valley diet credited with boosting energy and prolonging life — and it was one of the hardest things I’ve done

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 hot new 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. 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 — so long as it doesn't fall outside the designated eight-hour window.

Here's how it went.

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

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 that the most scientifically supported benefit of intermittent fasting is weight loss.

To this end, 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 that 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.

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 "HVMAN" skip eating on Tuesdays and claim they get more work done on that day than any other.

Varady said that hundreds of people in her studies have 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 some advice from other IF fans, I chose to break my daily fast at 12 p.m. and stop eating at 8 p.m., giving me eight hours to eat or "feed."

I wanted my last meal before my first 16-hour fast to be good, so I made one of my favorites: homemade pizza. I eat pretty healthy most of the time — for my favorite pizza recipe, I top whole-wheat crust with tomato sauce, a blend of cheeses, arugula, and chicken breast. I gobbled a few pieces and got ready to fast.

I started my first day of fasting with an iced coffee, since intermittent fasters are allowed to drink fluids during the fast. I added Splenda, as artificial sweeteners are also allowed. Sadly, however, I had to forgo any creamer or milk.

After drinking my coffee, I headed to my morning yoga class. I was initially worried about doing yoga without my usual morning fuel of Greek yogurt and cereal.

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

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

Finally, 12 p.m. arrived. I ate the lunch I'd prepared: a salad of spinach, chicken breast, mozzarella cheese, and tomatoes, plus a banana. I savored the sweet taste of victory. I had done it — my first 16-hour fast was over.

But I wasn't prepared for what happened afterward.

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 like I hadn't eaten in days. On a tip from a practiced intermittent faster, I went for a long walk.

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

I did notice one potential fasting-related benefit, though: around 3 p.m., when I'm normally yearning for coffee to stay alert, I felt as awake as I normally do around 10 a.m.

On my way home from work, the brain fog faded and I felt back to normal. Around dinner time, I didn't feel as hangry as I usually do. I warmed up a couple pieces of leftover pizza and skipped my usual dessert.

On most days between 6 and 8 p.m., I don't think about much other than what I'm going to make for my last meal of the day. But at 6 p.m., I was still plowing through work. And when I got home, my first thought wasn't about food. I relaxed, changed clothes, then popped the leftovers in the microwave.

The next day, I woke up determined not to be thwarted by yesterday's 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.

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 around 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.

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: traveling 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.

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 energized and happy — despite the fact that I'd also worked out in the morning and had hardly eaten.

Some of the intermittent fasters I spoke to told me that they prefer to workout in the middle of their fast since exercising in that state gives 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.

Still, scientists agree that more research on fasting and athletes is needed.

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.

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

When I took a bite, the flavor 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 realized 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.

I roasted the best marshmallows I've ever made, and didn't burn a single one! Knowing I couldn't eat them boosted my patience, making me a superior mallow-roaster.

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 stare at the breakfast spread.

There was fresh fruit, yogurt, and a plate of whole-grain muffins that looked like 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.

I didn't want to make the same mistake I had the day before by assuming that the timing would work out for me to eat lunch the second I was scheduled to break my fast. So I grabbed some nuts from the breakfast spread and saved them for later.

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 like 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.

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.

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 around 5, but wasn't hungry. It was a mistake I'd pay for later.

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.

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.

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-fueled urge to make s'mores. Armed with the leftover supplies from my work retreat, I fired up the stove.

By midnight, I'd eaten four s'mores and some vanilla ice cream, and felt like I could keep going. Only my lack of supplies stopped me. I love sweets, but this was abnormal even for me. It was like 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.

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.

Varady told me that not drinking enough water is 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.

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.

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.

I tried the popular Silicon Valley diet credited with boosting energy and prolonging life — and it was one of the hardest things I’ve done

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