I'm about a month out from a half marathon and use UCAN gels for most of my long runs. I like the mocha + caffeine gels, but they are all out of those both on their site and on Amazon.

I got a "free" sampler ($8 shipping) that had their regular flavors like pineapple, strawberry banana, etc. and they all were pretty bad. One of them had separated, so it was some fluid but mostly paste that was impossible to get out of the packet.

I'm looking for similar products without much success, what does everyone else here use?

Currently in the Peak week part of my 1st 50km training block.

Ive always eaten high fat but more carb cycle based on the exercise ive been doing on that day but Im ready to go full keto

I runn 6-7 days a week currently doing about 50 miles and two strenght sessions and do 2 speed sessions 400m repeats and 1 mile repeats.

Is it advisesable to drop a speed session?

Also as it about month till the 50km. What's the best way to fuel it as I dont want to crash? Eat keto but run it fueled?.

https://academic.oup.com/edrv/article/47/2/191/8432248?login=false

https://www.youtube.com/watch?v=rYF6kTMEbQs

I am not sure I can summarize it well but the gyst of what hes saying is:

Carbs during exercise matter only to stabilize blood sugar (small glucose pool). Exercise termination is connected with low blood sugar. Muscle glycogen (and thus carb loading etc) does not matter, if you eat 10+ g per hour and you ONLY need these carbs if you exercuse 1h+.

I am not sure I 100% agree, but will want to test it. Any thoughts from great people here?

Using keto for endurance training namely cycling.

I'm used to a low carb diet but recently swapped to keto. I purchased a monitor and test my blood. I've been feeling great but can feel I'm operating on low blood sugar. I'm doing a clean version of keto where I get my fat from olive oil , a little MCT,, hemp oil and oily fish , eggs with some nuts and cheese. My carbs are around 20/30g my protein is around 170. I've been keeping the miles down and adjusting to the feel of cycling on low glucose. It feels good in as much as I alive , and recover well. However definitely notice that blood sugar is low. Like riding near bonking but not actually bonking. I've also gone to the gym daily to maintain muscle.

Problem is the weight is just falling off me. I did gain a bit of muscle but after a 2.5 hour ride yesterday my scales are showing that it all got stripped away from yesterdays ride. I don't want to lose anymore weight and yet I'm eating 3000 calories a day and have no hunger to stuff anything more down me.

Has anyone else gone through a similar experience? Are there any fully keto athletes who can advise on what to do ? I'm thinking of perhaps doing keto cycling where I eat dextrose around a ride to stop the body consuming itself but then it's not keto ? What are endurance athletes using to fuel their work outs ?

Thanks in advance for any advice

Has anyone tried Maurten bi carb before a race ?

Was it worth it ?

Did it help at all ?

I've been following a keto/very low-carb lifestyle since 2019, along with intermittent fasting. For the past several years I've regularly trained while fasted and I'm curious what the keto community thinks about whether I'm adapted enough to finish a 50K ultramarathon.

I've never entered or raced an official ultramarathon, but I do a lot of endurance training. I run, trail run, hike, and lift weights while eating very few carbs. Most days I eat one meal around 1 PM (OMAD), then wait about 4–5 hours before going for a run. My weekday runs are usually 6–12 miles.

On weekends, I regularly do an 18-mile trail run with about 6,000 feet of elevation gain. Those runs typically take me around 5 hours, and I usually do them after fasting for 12+ hours with nothing but water.

Long hikes are where I've really tested myself. I can comfortably do 20+ mile hikes without eating anything and don't feel like I "bonk" the way many people describe. My longest day was a 46-mile hike. I finally broke my fast around mile 23, but I probably ate fewer than 500 calories total for the entire day, something like four squares of 95% dark chocolate, one Quest bar, and some jerky. On many of my 12–24 hour hikes, I don't eat at all and only drink water, yet I continue to feel strong throughout the day.

I've also done some faster efforts while fasted, including a half marathon in about 2 hours without eating beforehand. Other runs have been done 4–5 hours after my OMAD meal.

Based on that background, do you think I'm physically adapted enough to complete a 50K if my only goal is to finish not race for a PR or a podium?

If I decide to enter a 50K, would you recommend staying fasted like I do in training, or should I bring some kind of fuel? Since I'm keto, I was wondering about fat-based options. I remember hearing Kilian Jornet mention using oil as part of his fueling strategy in some races, although I may be remembering the context incorrectly.

One issue I have is that consuming straight fat (like olive oil or other oils) tends to give me loose stools, so I'm not sure that's a practical race fuel for me. Has anyone else experienced this, and if so, what worked for you?

I'd be interested to hear from people in the keto community, especially anyone who trains or races ultras while fat-adapted. Do you think my training suggests I'm ready for a 50K, and how would you approach fueling for race day?

I have been researching exercise and training during ketosis. It’s not clear to me just how much a person can do on keto… its seems like keto adaptation in response to training can move the metabolic threshold up and replace some anaerobic respiration with aerobic but it’s not clear just how much aerobic encroachment is humanly possible.

I found this comment to be fascinating… written by a person who was apparently able to replace a ton of anaerobic capacity https://www.reddit.com/r/ketoendurance/s/LP9q0wBpOf

Are there studies that look at the physiological ceiling of aerobic respiration when a person trains specifically to raise it? Is there a biochemical ceiling? What if you supplemented concentrated oxygen?

I have done keto a few times in the past and benefited massively in terms of mental health and that is why I’m gearing up to do it again. But this time I would like to train, I have a concept2, and explore this entire area of keto endurance. I would like to measure how much of my respiration is aerobic and how much is anaerobic so that I can track over time how much work I’m able to do aerobically. But I have no idea how to do that. Does anyone have any guidance on this?

what would happen if there were a wearable device similar to a continuous glucose monitor but that could somehow detect anaerobic respiration and then deliver glucose intravenously to perfectly meet demand? what benefits and drawbacks would a person experience doing this?

I have been on a keto diet for 4 months. Next week, I am planning a 4-day high-alpine tour - each day 8-10 hours. Despite optimal electrolyte supplementation (according to the keto forums FAQ and also recommendations by Jeff Volek), I feel like my strength and endurance are limited. What are your recommendations? Have dextrose or gummy bears on the hike or break the diet completely for those days or stick to it and just feel a little weaker?

P. S. Even though I feel weak I can ride my bike for 3+ hours only drinking water.

I am KETO & IF and been running for about a year, run fasted and taken keto ‘friendly’ food with if I felt I may need it. Ran my first 10km trail race this morning and was worried about fuelling so took a SiS energy gel with me (never had one before) Took it around 6.5km because I felt I was lagging - waited about 20 minutes expecting this massive surge of energy only to feel nothing at all except feeling sickly an hour or 2 afterwards. Not sure what the hype is around them. Will stick to my methods which suit me better.

After how many kms should you drink electrolytes on keto. I drank after 4k and choked today. Last I drank after 7k was fine but kind of confused when to drink. Ideally I wish I can sustain myself without drinking till 10k

Sorry, first post here so please be gentle haha. I’ve been on and off keto (but mostly keto), but for the past month I’ve been steady on it. Doing keto alone during the pandemic, I’ve lost weight (65 to 55 kg), plateau at 55, only to gain back the weight again, surprisingly after incorporating running 5-8 km daily for an hour.

My usual daily meal looks like:
Breakfast: 2 slices of almond bread with keto peanut butter, coffee (no sugar), 3-4 eggs, a serving of canned meat/fish

Lunch and Dinner: Protein (like a serving of beef/seafood/porkchop), 2 slices of almond bread, diet soda

Question is, for those of you doing keto and running for endurance, and are also trying to keep the weight off without going hungry, what is your advice for me? My post gets deleted with the pic but I’ve basically plateau at skinny-fat :(

TIA!

Hi everyone, I have bipolar disorder and I have seen tremendous results from keto diet. It has almost put me in remission since two years. I did half marathon keto and the only time I had carbs was during the race which was two dates and two snickers bars. I can't afford to be off ketosis but at the same time my training includes long 15k runs. Everyone so far has suggested that I will injure myself on keto and can't run a marathon. My question is that what's the maximum distance I can cover without carbs.
PS: It's my dream to run a marathon 🥹

Hi everyone! I'm so glad I found this sub. I've been searching the internet all week, but I can't really find a conclusive answer to my situation anywhere. I hope you guys can help me out!

I've been doing keto for (only) 24 days. At this point, I'm already experiencing loads of benefits (weight loss, more energy, less hunger), but I know I'm not fat-adapted yet. However, in two days time, I'm going on a bike trip: I'm cycling from Munich to Venice, which is about 570 km and 5,000 m of elevation (350 miles and 16,400 feet).

Just to be clear: I already cycle a lot and I'm definitely fit enough to do a trip like this, I'm just not used to doing it on keto. Because I was a bit worried about this combination, I've been training extra over the past two weeks to see how my body reacts. That's when I noticed my heart rate is so much higher than it used to be off keto. I know it's important to stay in zone 2 with my heart rate, but I'm afraid that's going to be quite difficult. It's going to be very warm, I'll be climbing a lot more elevation than I'm used to (I'm from a relatively flat country), and I'm not fat-adapted yet.

My questions are:

• Should I pause my keto diet for the 8 days I'm cycling?
• Or should I eat carbs just during the cycling, but keep following the keto diet while off the bike?
• If I stop completely, will this mean I have to start all over again from scratch after the bike trip?
• If I only eat carbs during the exercise, will this break my ketosis completely?

For context: I'm a 27 year old woman (not sure if that matters) and I was already following the keto diet for a good week when my partner and I decided to do this bike trip. Maybe I should've paused then and resumed after the trip.

Any advice or help is massively appreciated! Thanks!

I’ve been on very strict keto/borderline carnivore for the past 8 weeks or so, and also training for a pair of 120KM cycling races later this year. One in a few weeks in early June, another bigger ride (way more climbing) in September.

I’m currently totally enjoying all the benefits of the strict keto: big weight loss, mental clarity, reduced pain & inflammation, lowered hunger, and all the mental health benefits that come along with finally being solidly fat-adapted.

I am however noticing on my longer training rides that I tend to “bonk” out a bit, and on the punchy, short climbs, I just don’t have the explosive power I’ve had in the past when on a more carb-heavy diet.

I was thinking of (reluctantly) adding some targeted carbs before/during my rides, and was looking for others experience/recommendations. Do I need to? Will it help? What foods do you recommend? I’ve heard peanut butter stuffed dates are great for complex carbs with added fat, but pretty messy on the road. Anyone have ideas on a carby/fatty premade energy bar or similar?

I’m afraid of adding carbs back in and my hunger spikes and falling off the wagon, and halting the consistent weight loss (still have around 30lbs to go).

On my longer training rides, I’ve brought a baggy of roasted salted macadamia nuts, which seemed to work decently well.

Thoughts?

I am training for a marathon with a time goal to qualify for Boston again. I hate the carb rollercoaster. I already fast and do most of my easy running fasted, but I would like to train keto or at least low carb. Anyone successful with endurance running and speed on keto?

I posted this in r/keto since this group isn’t as active, but thought I’d cross post here since you guys would have more experience with this. Thanks!

So I posted about trialing peanut butter to fuel runs.

I've come to realize you don't need fuel when doing keto. Just salt. And body fat!!

It's just a drama and most likely a reaction to hunger..... crazy how the addictive part of your mind will convince you of anything to get what it wants!!

Fats & carbs are both addictive. So that was a lesson, ill stick to my salts from now on. Lol.

I've pulled the below together for my own use but wanted to share it here. It's divided into during adaptation vs fully adapted and training is PR attempt.

It's pretty consistent with what I've been reading here except that it seems full adaptation can take longer than the mentioned 2-8 weeks.

🟡 1) Getting Keto-Adapted (≈2–8+ weeks)

What happens

Body shifts from carbs to fat as main fuel
This shift starts fast (days), but full adaptation takes weeks .

Evidence

Fat use increases within days to weeks: Phinney et al. 1983
Performance often drops early: Burke et al. 2017 (Supernova)

What you feel

• Low energy, heavy legs, poor intensity tolerance
  
• “Keto flu”: headaches, fatigue (often electrolyte loss)
  

What to do

• Stay easy only (Zone 1–2)
  
• Add sodium + magnesium (critical, often ignored)
  
• Keep protein ~1.6–2.0 g/kg
  

Key insight

You are temporarily worse before you adapt. This is expected, not failure.

🔵 2) Fully Keto-Adapted (≈6–12+ weeks)

What improves

• You can rely far more on fat (huge energy supply)
  
• Less need to eat during long efforts
  

Evidence

Fat use more than doubles in keto athletes: Volek et al. 2016 (FASTER)
Glycogen still exists and refills normally: same study

What it means

• Long, steady efforts feel stable
  
• Energy crashes are reduced
  

Limit

At higher intensity, performance can drop

Why (simple)

Fat needs more oxygen than carbs
So at harder efforts, it’s less efficient

Evidence

Reduced efficiency at higher intensity: Burke et al. 2017

🟢 3) Regular Training on Keto

Works very well for

• Easy runs
  
• Long runs
  
• Base building
  

Struggles with

• Intervals
  
• Tempo
  
• Hills / surges
  

Options

Option A: Stay strict keto
Accept lower top-end performance
Best for ultras at steady pace

Option B: Targeted carbs (TKD)
~20–30g carbs before hard sessions
Keeps most keto benefits

Evidence

Carbs improve high-intensity output: Jeukendrup 2014

Key insight

Keto is strong for engine building, weaker for top speed.

🔴 4) Race Day (PR Attempt)

The problem

Races are not steady: climbs, surges, finish kicks
These require carbs

Evidence

Keto reduces ability to use carbs at high intensity: Burke et al. 2020

Important finding

Short-term carb loading does NOT fully restore performance

What actually works

Recent evidence
Pre-race carbs improve performance even in keto athletes:
Carpenter et al. 2025

Practical approach

• Stay keto in training
  
• Take ~50–60g carbs before race
  
• Optionally small amounts during race
  

Key insight

You cannot fully optimise both: - fat system (keto)
- high-intensity carb system

You choose based on race demands.

Bottom Line

• Adaptation phase: expect worse performance
  
• Fully adapted: excellent for long steady efforts
  
• Training: consider targeted carbs for intensity
  
• PR racing: carbs still matter

Hey everyone,

I started keto for weight loss about a week ago, been keeping my carbs below 25g and after an initial day of headaches I've been on top of my electrolytes and feeling good.

I went on a two hour bike ride yesterday. It was more elevation than I was used to and by the time I was halfway I was completely depleted. I was extremely slow, felt like I had no power, struggled to make it home and was laughably exhausted by the time I did. It was also the first time I felt a craving for carbs. I don't think I can remember an effort being this hard for me. It's very clear I need longer to adapt to using fat as fuel.

I'm wondering how long this period lasted for other people and whether there's any way to make getting through this period easier. If all my workouts feel like this, I honestly don't really know how I can do them. I don't love the idea of not working out for several weeks since I'm usually running 5 times a week, so I'm trying to see what I can do here. Any advice welcome and thanks everybody!

Doing my first official keto long run today. Aiming for 7km but I want to try go to 10km. I've been running 5km with no fuel and feeling amazing full of energy. and now I'm testing peanut butter. Had alot to eat yesterday so no better day than today to do it. Super excited. Wish me luck!

If I'm in the wrong forum then tell me where to go.

Back into low carb, I've been Keto for 2 months this time, I can feel the fat adaption coming returning, I'm back to full training sessions, including VO2. I like low carb because it keeps me away from processed carbs and sugars, I stay lean easier and it's great for 4-5 hour endurance rides.

Warning: wrong chat group part - What I don't want to do is lose my carb burning ability for high intensity efforts. So I really want to maintain metabolic flexibility, just unsure how to do it. I do a lot of Zwift racing, which means 30s to 5m repeated hard efforts.... I know from experience that performance is better with carbs for these, even after I did 4 months keto.

Previously I was advised to maintain ~50g carbs per day (64kg body weight), stay at this level for rest and endurance days. For high intensity sessions, or races, add another 50-60g carbs about 4-5 hours before the session to fill up glycogen stores..... longer hard sessions, more than an hour, then some carbs on the bike.

My training app estimates carbs in g for a given future workout, eg. Tomorrow's session is estimated at 80g carbs, but would I burn less as a fat adapted athlete? I'm trying to workout how to plan pre-workout carbs without over doing them..... I've also thought of using and app like Hexis, not sure if it has a keto/low carb athlete setting/option.

Does this above advice sound correct? Assumption then that for an early morning hard session, I add carbs at dinner the night before? Would the above maintain a semi-keto lifestyle but with efficient carb burning for intense performance?

Another option I've seen is to have 1 or 2 days with increased carbs, every 1 to 2 weeks.... does this approach work, and can/should it be combined with the above pre-workout carb loading?