This Fruitarian Can Fly

During one five-month stretch in 2012, a New York City software entrepreneur named Michael Arnstein finished 16th at Death Valley’s Badwater 135, placed 13th at the Vermont 100 later that week, came in fourth at the Leadville Trail 100, ran Greece’s 246K Sparthalon, won Arizona’s Javelina Jundred and, at the Desert Solstice Invitational Track Meet, ran 100 miles in 12 hours 57 minutes 45 seconds.

He ate nothing but fruits and vegetables (and the occasional gel) the whole time.

Arnstein had had success as a cross-country runner in high school, but skipped college. He married at 22, and by age 25 he had three children. The demands of work and fatherhood left little time for exercise, and he soon grew overweight.

Then, spurred by regret at missing his chance for athletic glory in college, he returned to running. He started with marathons, but quickly gravitated toward the trails. “In high school I read an article about the Leadville 100,” he says. “I thought, ‘How in the world can someone do that?’ … The seed was planted.”

As Arnstein ventured into longer distances, his competitive urges returned. Already a vegetarian “for ethical reasons,” he gradually pared down his diet: First he cut junk food, then bread, grains and legumes, until, by mid-2008, only fruits and vegetables were left.

“I was eating pounds of food, whenever I wanted, but still losing weight,” he says. “I felt clean and light.”

Arnstein credits the nutrient-rich diet with speeding his recovery, allowing him to log 200-mile training weeks without injury. Within a few years, he clocked a sub-2:30 marathon, won his first road ultra and ran Leadville in under 24 hours.

Recently, Arnstein has backed off racing somewhat to devote more time to family and work. Now 39, he lives in Kailua, Hawaii, with his wife and kids, where he directs a software company and runs a more modest 60 miles a week—still good enough to win Hawaii’s grueling HURT 100 in January 2015.

Arnstein on the Fruitarian Life

People assume I am some barefoot hippie. I am not. I am a New York businessman with a Lamborghini. I was doing this to win. And it worked.

I don’t eat meals. I graze all day. The idea of needing a protein, a starch and a fat to make a balanced meal is false. In nature, animals eat what’s around, whenever they want, and they eat one thing at a time. We don’t need a lot of diversity per meal, so long as we get it over time.

Raw fruits and vegetables have lots of amino acids, which our bodies quickly assimilate to build our own protein. This translates into a fast recovery time. That’s how I was able to run such crazy mileage every week without getting injured.

Forget the protein shake and drink carrot juice after a big run. You are going to levitate.

I get regular blood tests, and, so far, vitamin B-12 is the only nutritional supplement I’ve needed.

I don’t use sport powders or shakes, but I do use gels—only when racing. It is hard to carry the volume of fruit I would need to fuel myself during a race. I experimented with dates, but eating a lot of dried fruit and drinking a lot of water means lots of trips to the bathroom.

Socially [fruitarianism] is hard. Not many people eat this way. I am not a fun guy at a barbeque.

Be prepared for some detox effects. When I first switched to the fruitarian diet I developed a skin rash, which went away after a few weeks.

My wife is on a largely fruitarian diet. Our kids eat whatever they want. We don’t force it on them, because they have to make their own decisions.

My racing schedule was unsustainable with a full-time job and family—with nearly 20 races a year, I was gone most weekends. I’ve cut back to only five or six races a year, training around 60 miles a week.

Since I am not racing as much, I’ve also eased back on my diet. I still eat mostly fruits and vegetables, but I’ll go out to dinner one or two nights a week and order a rice or veggie dish. If my wife makes something like baked potatoes or a bean salad, I’ll have some. I don’t beat myself up. It tastes good, and I enjoy eating with family and friends.

Ask the Dietitian: Is a Fruitarian Diet Right for Runners?

Though a few athletes, such as Arnstein, may find success as fruitarians, such restricted eating won’t meet most athletes’ dietary needs, according to Maria Dalzot, a competitive mountain runner and registered dietitian who writes an online nutrition column for Trail Runner.

“A 100-percent fruit-and-vegetable diet is essentially an all-carbohydrate diet with minimal amounts of low-quality protein, meaning that one or more amino acids are missing,” she says. “This diet is also extremely low in fat, which is an important component of an endurance runner’s diet for energy sustenance and vitamin absorption.”

In addition, fruitarians may have a hard time getting essential nutrients like omega-3 fatty acids, calcium and vitamin D without supplementation—and even that isn’t always effective. Most supplements won’t replace the proteins and fats missing from fruits and vegetables, and the micronutrients in pills or powders are not as easily absorbed as those found in whole foods.

“Supplements can provide a false sense of security to individuals following restrictive diets,” says Lindsey Tucker, a registered dietitian and trail runner based in Minneapolis. “They can believe they are covering all of their bases, when, in actuality, their bodies may be inadequately nourished.”

So, before you switch to a fruit-and-veggies diet, consider whether it can meet the increased caloric and nutrient needs that come with training. And, says Dalzot, don’t forget to ask, “Are you going to be satisfied with this style of eating, or feel like you are missing out due to its restrictive nature?”

This article originally appeared in our June 2016 issue. You can find more stories about nutrition for runners here.