Run Fast AND Long With Zach Bitter

Run Fast AND Long With Zach Bitter

Zach Bitter is an extraordinary ultrarunner. In 2019 he broke the 100-mile and 12-hour world records. He follows a largely ketogenic diet so we're keen to hear how he runs so fast for so long while low carb

In 2019, Zach Bitter did something quite remarkable: he ran 100-miles on a 443-meter indoor athletics track in a mind-blowing 11 hours, 19 minutes.

That's an average pace of 06:48 minutes per mile...for 100 miles! Or, put another way, four sub-3 hour marathons back-to-back.

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Alongside his extraordinary running achievements, Zach's known for his low carb, high fat approach to training and racing nutrition.

In this podcast, Zach shares his training methodology and his well-educated insights into sports nutrition and high performance on a low carb diet. You’ll also hear him speak about how you can safely give this approach a try without jeopardising any upcoming races.

Listen to Zach on the 33Fuel podcast

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Or watch the live recording on our YouTube channel

Zach Bitter podcast: show notes

Zach Bitter on running solo

Zach logs some serious miles, predominantly solo. Why does he choose to spend so much time alone?

It’s not that I’m trying to avoid people. But I found out I could kill two birds with one stone by running alone: I enjoy learning so I’ll listen to podcasts while running. Secondly, it’s just life routines. It’s tougher to find a time of day that works for everyone.

"I have a lot of flexibility of when I run, so I tend not to operate on the extreme ends of the day. I get out in the more traditional work hours”.

Zach Bitter on ultrarunning and community

The unique thing about ultrarunning is the that the community is so inviting. It’s really easy to see what everyone’s doing to get ready for an event”.

On one hand, that’s great because access to information and sharing is valuable for beginners. But it also makes it very easy for new ultrarunners to follow plans which they’re not physically ready for.

You’re asking a lot of your body to go from not being an endurance athlete to racking up 100+ mile training weeks. But there’s also a big mental component – it’s not easy to stay focused mentally all day long. It can be hard to keep the desire”.

Indeed, it’s not uncommon for ultrarunners to exit the sport due to mental burnout rather than for physical reasons.

We do see chronic injuries in the sport but I think that’s probably more due to poor mechanics or neglecting the tertiary things to keep your body healthy outside of running itself”.

On Zach’s own podcast – Human Performance Outliers Podcast – he’s learnt from a much bigger field than just within the ultrarunning community.

Zach Bitter's take on the low carb, high fat ketogenic diet

Zach followers a low carb, high fat ketogenic diet.

I used to follow the traditional high-carb diet (60-70% carb) and it wasn’t like I saw a reduction in physical performance.

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"It’s more than I was noticing a lot of other things occurring outside of the actual running itself. For example, when I first started getting into ultras, I started to notice the further I got into the sport, the harder it was to sleep consistently. I’d wake up three or four times per night and it’d take 15-20 minutes to fall back to sleep.

"I ended up having to schedule a 10-hour block of sleep time in order to get the actual 8-hours needed.

"I had huge ebbs and flows of energy throughout the daytime. It’s a difficult place to be [as a middle school teacher] and I thought they just weren’t common things for someone in their mid-20’s to be feeling”.

Zach was averaging around 15 hours training per week, peaking at 20-hours.

Basically, over the last decade I’ve averaged just over 5,000 miles per year. Which is an average of 100-miles per week. So, I certainly sit in the high volume training methodology”.

I’d say!


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If you're going to go low-carb, ensure you're getting all the nutrients you need to fire on all cylinders. Just one daily spoonful of Ultimate Daily Greens provides powerful antioxidants and alkalysers to keep you in tip top shape, ready to perform

But before making drastic training changes, Zach explored other avenues. He began listening to podcasts, learnt about sports nutrition and soon discovered the high fat, low carb approach.

I’ve been doing it [high fat, low carb] for about 8 years now [alongside high volume training]”.

For me, the real ‘ah ha’ moment came when I started implementing a high fat, low carb approach. I was thankfully aware enough that the best time to do that is during the off season when you’re not focusing on intensity and training volumes are lower. So, I dropped it in and let my body get used to it before I dove into a strict regimental program.

"What I noticed almost immediately is that my sleep quality improved”.

Zach also noticed his energy levels balanced. No dips, just a level output throughout the day.

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200 laps down, only 202 more to go. Zach hits up the US 100-mile record in fast style

Becoming fat adapted - Zach Bitter's tips

A key metric of the ketogenic diet is that carb intake is restricted to 50g per day. But Zach doesn’t think that works for endurance athletes. The reality around fat adaptation is that it’s a sliding scale. It’s not an all or nothing.

I think it’s beneficial to start out strict to those parameters [50g per day] and let your body adapt but then once you get back into the flow of training, I think 100-150 grams per day carb is probably a better starting point”.

How to become fat adapted

Zach always asks: “How fat adapted do I need to be to maximise performance? And the answer might change depending on the goal.

"You have to keep an open mind and listen to what your body and performances are telling you along the way”.

Looking for a low-carb, high fat energy gel? 

Well step this way. Our unique 4-ingredient Chia Energy Gels were developed in Europe's toughest ultramarathons for strong and stable energy, great taste and zero stomach issues. 

Zach's fat-adapted field test

“When it comes to fat adaptation with extreme endurance, I’m more inclined to have someone do a field test. It’s going to be indicative as to whether the approach they’re doing is working or not. When they’re doing substantial training, I’ll send someone out for a 5-hour run and if they feel their energy levels are solid with just water and electrolytes, then you’re fat adapted enough. You don’t need to become more fat adapted”.

Zach Bitter - keto diet and lifestyle

If you’re trying the ketogenic diet for lifestyle purposes – ie, you have no athletic goals linked to the shift – then clearly attempting a five-hour run isn’t going to be the wisest move.

In that instance, you can learn how fat adapted you are by fasting for a 16-hour. If you don’t feel like an emotional wreck, at the end of your tether and you’re not hungry for every minute, then you’re well on the road to fat adaption.

Read our Beginner’s Guide to Intermittent Fasting

Why what you’re training for matters

When it comes to the ketogenic diet, mindfulness around the event you’re training for is crucial.

Zach’s carb intake varies depending on his training and race goals. We love that he’s not dogmatic about being keto and that his choices are led by improvements in performance above all else.

As soon as I can’t hit key workouts which I deem necessary due to nutrition, that’s the day I switch my nutrition”.

Exactly how it should be.

At 33Fuel, we’re on the same journey. Our origin lies in the foundation that ordinary sports nutrition didn’t sufficiently fuel our performance goals, and it was damaging our health ones.

Back to Zach:

“If you look at my entire year – 365 days – I probably average 10% carbohydrate intake”. That doesn’t mean that every day Zach’s only consuming 10% carbs - it means that some days might be 30% and others may be 0%.

“I certainly don’t see carbs as this demon thing. I see it like caffeine. If I can get the same output on 10% as I can on 60-70%, then that’s win win for me”.

Zach Bitter’s go-to foods

On switching to a keto diet, Zach says “It’s a matter of finding what food will keep you on track. There’s no point making it super-hard for yourself and falling off the wagon within weeks”.


He bases all his nutrition around animal products – fatty cuts of meats, grass-fed beef etc – and he enjoys these so doesn’t find it challenging. As with all ways of eating, sustainability is crucial for longevity.

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Zach Bitter on the future of ultrarunning - how fast can it get?

Zach thinks that within the next five or ten years we’ll see a sub-11 hour 100-miler.

We’re getting more guys who have run a sub 2:15 marathon get curious about ultramarathons. And not looking at it from a perspective of a “death jog”. It’s about getting that talent pool as deep as possible that’ll break barriers.

There’s only one person in North America right now who can go to Western States and say ‘I’m just going to match the next fastest guy’s pace and then do what I have to take the win’. And that’s Jim Walmesley”.

He’s a little unique though!”

Zach Bitter podcast: conclusion

Zach is a knockout example of someone pushing performance boundaries by taking an uncommon approach and developing new and winning strategies over time, effort and practice. We love his take on life and performance and think this conversation has tons to deliver for athletes everywhere who are looking to raise their game.

Here at 33Fuel we're all about bucking decades-old trends and dogma in sports nutrition to deliver results that aren't just a step forwards, they're a leap forwards. Just because you’re told by marketing wonks at sports nutrition companies the world over that you need to consume 60-90g of carbs per hour, we strongly encourage you to ask yourself how that works for you, how it makes you feel and how your performance is as a result.

And if it doesn’t work for you why continue with it? If you experience peaks and troughs in energy, a dodgy gut or simply don’t enjoy your sports nutrition as real food, then it might be time to explore alternatives.


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Whatever your sport, fuel yourself with nutrition that's both great for performance AND health. All 33Fuel products are 100% natural, use only the highest quality ingredients and taste fantastic. Do your body, mind and performance a favour and give us a try today!

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