Ultra Endurance Athlete Starting Keto


(Nathan Toben) #1

Hello all.

I’ve been reading the forums every night this week as I start Keto and thought I’d lay out my circumstances and intentions in hopes of minimizing the amount of mistakes I will most surely make embarking on this endeavor.

I “workout” 50-60 hours a week. That is right. 50-60 hours. I am a food courier by day and by morning and weekend I am an ultra trail runner. My runs are aerobic (right now) and my work delivering food on bike is variable aerobic/anaerobic.

Biking = 36-40hrs/week.
Running = 12-18hrs/week.

These variables are fixed and so any suggestion to “do less,” while I appreciate any advice, will fall on deaf legs.

I am 7 days in to my first honest foray into fat adaption.

I am 5’10, 165lbs, 15% body fat (according to this scale in my house which is probably off by ±2-3%). I have been a food courier for 2 years and an ultrarunner for 4 years having completed 1 50k, 2 50-milers, and 4 100-milers.

My 100-mile PR is 21:57:05 set on a 96deg at altitude.

My interest in Keto stems from the fact that I am 33 years old, single, truly in love with endurance and I want to commit to my health more substantially to change my body composition so that I can soar down mountains and ascend with greater ease. THere is no better feeling in my life than that.

So. I have been eating about 2% carbs, 70-75% Fat and 20-25% protein. Needless to say that with my workload and this macro breakdown, I have been bonked all week. Headaches for the first couple days, mental fog for the next couple and it still lingers, and both my runs and my shifts on the bike are suffering. This I expected and I am more interested in making an expedited transition to fat adaption rather than a protracted one with slightly better training/work.

What I want to know from you all is just what advice you have for someone in my scenario. I’d really appreciate it if you respected that the running and biking are fixed variables and maybe if you could put yourself in my shoes, with your wisdom and experience, and tell me what you would do so that I am nourishing my body, aiding in adaptations, and gradually moving towards lower body fat %. How should I reintroduce carbs?

My current foods (eggs, oils, meats) are very plain so to help kill off bacteria left over from the sports nutrition of my last 100-miler. I am not of the mind to fuel with fats during my events. I will continue to do my overdistance runs training with complex carbohydrates but my meals before and after will be very low carb or zero carb. That said, for this adaption phase, I will withhold from those race fuels for the next month or so as all my miles will be at MAF (aerobic) paces.

For someone with my workload, I imagine if I am properly fat adapted, my system may be able to utilize well-timed carbs up to 100-200g carbs/day and stil remain in ketosis. At least this is what I have gleened from the limited amount of stuff I can find.

I am just also grateful to have found you guys and read your stories of progress and transcendence. I am also a person in recovery and have found that when I remove sugar from my life and start to fuel on ketones, my mental sobriety increases noticeably. Just a side note there.

Anyways, hello. My fellow trail runners call me Steep. I’m keeping calm…and I’m all ears!



(LeeAnn Brooks) #2


You’re level of athleticism is wayyy past my league, so I won’t insult you by offering any running tips😂.

I have a good friend who does ultras and I tell her I want to be like her when I grow up. Right now I’m just aiming for my half marathon.

I will tell you the one thing I discovered with Keto and running is that when you think you’ve gotten enough sodium in, you find out quickly when you haven’t. I would get post run nausea almost every run whenever I would increase miles, even when I would take some leading up to the run. I found I needed to ingest more as soon as my run was complete to ward of the nausea.

I bought sodium tablets to carry with me on runs just in case. With doing such long runs, I imagine you will need to find ways to get your electrolytes replenished while you run. I’m sure you’re used to that anyway, but you will be shocked at how quickly Keto will deplete them even without adding grueling exercise.

Again, welcome to the forum.

(Edith) #3

I would suggest reading “The Art and Science of Low Carbohydrate Performance” by Phinney and Volek.

Also, definitely salt, salt, and more salt. Low carb is diaretic. On very low carb your kidneys no longer have the need to hold onto sodium so it needs to be replaced throughout the day. I am sidelined from running at the moment, but even so, (I am not even close to your level) with my low activity I need about 5 grams of sodium or 2 teaspoons of salt a day. I would imagine you would need quite a bit more.

Your performance will definitely suffer for several weeks as your body learns to use fat instead of glucose for its energy. You will gradually notice that your muscles feel less and less lead-like as the weeks progress. I can’t tell you how long that will take since everyone is different.

Those are the only words of wisdom I have for you. There are endurance athletes on this forum who, I’m sure, will weigh in.

Good luck!


Hi Steep, Hope your experiment into keto is going well. I personally believe that being fat adapted will help you in the long run. If you do not already have it you may want to install something like Cronomter on your phone in order to keep track of your micros and macros. Hope you are staying away from the processed foods also. I have gleaned from my research that endurance athletes have alot of problems with their gut so this keto diet may help you there but it is very individualized. Please keep us posted on your progress? Thanks.
I have been low carb / on off keto since 2014 and run mostly half marathons. Currently I am getting ready for a full marathon in November and still have not decided on a fueling plan. Thinking about consuming waxy maize starch, BCAAs, electrolyte tablets, salt and water. My half marathons are usually in a fasted state and all I need is water and salt but this marathon will be a faster PR so I will need glucose.

(Nathan Toben) #5

thanks @Ketoe , I track stuff every now and then on MyFitnessPal, what does chronometer do? i’ll check it out. yeah gut issues are part of the reason I gravitate to lower carbohydrate intake. Indigestion has gone down markedly since a month ago. Excited for your full. what is waxy maize? is this similar to the slow-release starch in UCAN? I have used UCAN in the past to mixed results. It does not seem to be a solution for races lasting 20hrs. I too will be using sugar in my racing and look forward to seeing how my body metabolizes as much as 200g/day during peak training and seeing how long it takes to return to ketosis.

(Bunny) #6


(crawford walker) #7

Hi Steep,
I’m a 73 year old trail runner. I started keto 8 months ago. For the first 6 months my ketones were around 0.5 but have been higher since I started intermittent fasting. I don’t eat after dinner and eat a late breakfast so I have at least 16 hours without eating.
I run in the mornings without eating first. I am fine on water alone for up to 3 hours then I start to feel a little weak so will eat either a small handful of nuts or a slice of cheese. I think cheese works best. I tried gels but they didn’t seem to work.
I have not done a race on keto. My problem for racing is that my aerobic threshold is around 125 and it’s hard to run at any speed at that heart rate. I don’t think I can make the cut-offs on a ketogenic diet. Long races would probably be OK but I have never done more than 50K and I’m not too interested in starting at my age.
I have had some problems with calf muscle cramping which I think may be due to electrolyte depletion so keep up the Mg K and Na.
You have a very active lifestyle and I think keto will work well for you. Make sure you eat enough as you won’t get hungry when you’re in good ketosis.
Good luck,

(Nathan Toben) #8

hey crawf, I recommend taking in Saltsticks or S Caps, 1-2 an hour since us low carbers jettison salt. Also, for races, I suggest Vespa Nutrition and also still taking classic carbohydrate. Since I am an addict, this is tempting the dragon but it is more worth it to me to excel at my passion and having that strong “Why” eclipses the cravings that come afterwards. For hundred-milers I consume many many carbohydrates. For a 50k I consume 2-4 gels. for a fifty miler it might be 4-10 gels. I don’t see why you couldn’t run longer distances with the proper preparation. Inspired by you, nathan


I was listening to/reading Zack Bitter’s stuff - he’s a low-carb athlete, does ultramarathons.

What was interesting - the ONLY calories he consumes during races is carbs. He said there’s no point in consuming fat, as it metabolizes too slow to come into play, better to just depend on what you already have.

Example interview… dude’s a machine.

“On race day, I rely on body fat for my fat fuel as a way to bypass the digestive processing of fat. It’s a common misunderstanding that lean athletes don’t have enough fat to fuel an event
Even when I’m at my leanest, say 5% body fat, I have enough fuel in that tank to get through an ultra-event. The fuel supply that is finite is glycogen, so that’s what I replace during an event. The biggest difference from when I was high-carb to now is that I need much less to meet these needs. I typically hit 150-250 calories per hour during a race from mostly Xendurance Fuel-5 and Hydro-X. In the past, when I was high-carb, I’d routinely take in 400-500 calories per hour.”

(ianrobo) #10

just wow in what you do @Nathan_Toben and looks like you are perfect for Keto and fat adaption as a lot of you stuff is done in zone 2 HR etc for obvious reasons.

just one question in this, do you have any recent bloods to share would be fascinated to see them ?


Hi Nathabn,
I ended up using Vitargo (unflavored) during a marathon and found it to be excellent. It was recommended to me by Dr. Mike T Nelson (hope I got the name right). Found him on the Nourish Balance Thrive podcast and messaged him on facebook.

Dealing with a plantar issue now.

Hope all is well.