A few questions about fasting rides (fasted training)

@Djf500 To become fat adopted in that timeframe (2 weeks to 6 months), did you do this every time you got on the bike? Even if the workout called for VO2 Max intervals?

Absolutely. The 1st couple of weeks of LCHF (low carb, high fat), while your body is learning to run on fat instead of just sugar (carbs) are a little rough. Your energy may dip during your daily activities and you’ll feel it on the bike during hard intensities. There’s little tricks, like drinking water just before you ride and adding electrolytes to your water (not sugar… just minerals… there’s several good products out there). I learned a lot from the book I mentioned.
Winter or off-season is a great time to do this. I switched in the middle of the riding season which wasn’t super smart :slight_smile: Ideally, I’d time the dietary switch with some down time or at the very least, sweet spot 1. Exercise will help you adapt quicker but don’t get discouraged if you dip in efficiency at 1st it’ll come back. The longer you go, the more fat adapted you’ll be. You can absolutely do VO2 Max intervals after a few weeks. There’s tons of videos and podcasts about keto. Youtube has a ton of free info and the book “The Art & Science of Low Carbohydrate Performance” is an easy read and invaluable resource since they’re really talking about endurance athletes… so it speaks directly to what we do. And they have the science to back it up. Ultimately, once you can run on fat, you’ll be ‘Dual Fuel’ where you can run/bike on fat for hours and you’ll still have your sugar burning system of course so if you do take a gel… it’ll be like rocket fuel! I haven’t had a gel in about a year probably… but I don’t race. I could see it coming in handy for the last push in a race or something like that. Or even just to use as you fat adapt if you’re really struggling. It’s been an awesome journey for me. So much healthier w/o sugar, cheaper (sorry Hammer Nutrition… don’t need you anymore) and I can ride without eating/crashing/eating/crashing. It’s a life style change but very worthwhile for those willing to put the work in.


Here is my opinion on this.
Maybe at the elite and pro level it may be useful but for the rest of us it is junk. The questionable benefits if there are any, are negligible. The 1% benefit you may gain, you will definitely lose on the course because of simple mistakes (equipment choice, wrinkles, getting out of aero 10s too much, fueling, etc). I put it in the category of altitude training. If you ever get to the point of needing it to win, do it. Otherwise listen to the pros who eat a hearty breakfast and then go ride.


I realise to am replying to this months later.

As I understand it, the presence of carbs/plentiful glycogen don’t shut down fat metabolism during exercise, but they inhibit the mitochondrial synthesis that is observed after fasted/depleted training.

If one of the goals of the training session is increased mitochondrial density then fasted/depleted training could be beneficial.

On the other hand, I might have completely misunderstood.

@Djf500 Is there a scientific way to empirically measure fat adaptedness? (besides your N=1 comment. I don’t mean this as a criticism. Genuinely curious.

1 Like

I agree. All that sugar over 20+ years riding is not good! As usual, there’s a big middle area between sugar all the time, and full Keto. You can absolutely become less reliant on sugar without going full Keto/fully “fat adapted”. The link in one of the posts above offers suggestions.

Yes - or at least, fat vs carb use during exercise can be measured. The standard way is through an RER test. I’ve seen some people post results of their tests on this forum, but I can’t find the post. It was very interesting. Showed a lot lower fat betabolism in the year the person had been on a carb heavy diet (if I recall).


Found it. This post highlights why for long rides you need to have robust fat metabolism. Awesome post by the way - thanks @konradkowara for sharing.

I love the TR product and podcast, but this is something I think the TR crew have not given enough credence to. A sugar and carb approach is great for 1-2 hour rides, and absolutely should carb load and eat during long rides, but to make it through long rides, you need robust fat metabolism. And the ways to train this don’t always align with just getting the highest FTP.

Take a look at the 2017 vs 2018 fat vs carb profiles for the person who posted this. It’s very telling. Imagine trying to do the LT100 with a profile like the 2018 one.


@ktimesk I don’t really think so. Though I’m not an expert, just someone who tried LCHF riding and found it really beneficial. You can measure keytones but it’s imperfect (and I don’t do it anymore though I did when I started). Really, you know your fat adopted b/c you can feel it. Once your burning fat for energy for awhile, you def know the difference. Mainly, you’re not hungry all the time, you can ride w/o sugar or calories in general and your mood is very level (no blood sugar spikes). There’s lots of other benefits which you can read about as well. It’s worth experimenting with just so you can burn sugar OR fat but there’s def an adjustment period which turns people off as well as changing your diet/eating habits which I understand can be challenging. My main point in posting here is that it’s possible and the discussion on the TR pod dismissing it was disappointing. You can’t do a fasted ride if you haven’t put the effort into becoming fat adopted 1st.

1 Like

@Davewh Interesting article. Less sugar (and carbs are sugar) in our diet and training is the key to long term health and most likely to a long riding career. That’s my opinion of course but it’s based on a lot of research showing that dietary sugar and not fat is actually the culprit in America’s obesity epidemic as well as a slew of other metabolic disorders. You don’t need to be ‘full keto’ at all. But to get the benefits of burning fat as a primary fuel source once and awhile at least, you need to commit to becoming fat adopted for a couple months. And chances are, you’ll like it. Then carbs really just super charge you but you can switch back to burning your own fat easily. There are slow digesting carbs like “Super Starch” out there which are pretty much designed for endurance athletes.


@DaveWh Thanks for finding that post. Very interesting. perhaps I should move some of my easier TR workouts in the morning and do them fasted.

@Djf500 Can workouts above threshold be done fasted? Or should I only do sub threshold workouts fasted? (In order to be fat-adapted).

Sugar burning works! You can do that for sure. I’m just saying there’s another way that could work without all the sugar. But until a pro comes out and shows their diet is LCHF, we won’t know how/if LCHF would work at the elite levels of riding. Do what works for you. I was just saying not to dismiss LCHF and fasted rides, even on occasion, based on the podcast discussion. There’s potential benefit in having access to both systems (sugar and fat burning).

1 Like

Nah - I like my carbs too much😁

For me, I know I would not sustain a LCHF diet. Instead, I’ve made the effort to cut out processed sugars and high GI carbs, and that has helped me become less reliant (ie not at all) on a gel or coke sugar boost to get through a tough workout, say, VO2max.

I’ve also switched my snacks to be nuts instead of things like toast or granola bars. So I eating an overall much more balanced macro nutrient profile now vs a year or two ago.

1 Like

You could do this approach.

Based on the below article, plus other research I’ve seen on long rides burning fat, I’ve been working in 4 hr endurance rides into my base training. Not that the benefits of this type of riding is really any new insight - this is part of the Eddie Merckx old school ”ride lots” approach, or the “you have to ride slow to be fast” approach.


@DaveWh Got it. Thanks for the link. :slight_smile:

That’s awesome. Great approach and sounds like a good balance. I’m nowhere near as low carb as many ‘hardcore’ keto folks… it’s pretty individual per your body but also being so active, we can handle carbs much better. So long as it’s the ‘right’ kind of carbs. Reducing sugar is really where it’s at.

1 Like

I primarily train and/or ride in the morning and I never eat before any training or ride. So I’m typically fasted for around 10-11 hours just from post-dinner & sleeping. I’ve done some really hard mtb rides fasted much longer w/o problem (not trying to do a fasted ride… just waking up later, driving to the trail, etc). I’m never hungry in the morning anymore b/c my body is burning fat from fasting overnight. To answer your question, yes you can do above threshold workouts fasted but my guess is that you have to be fairly well fat adopted. At least 2-3 months is my guess. And well hydrated. There’s a lot of talk out there that you lose your high end effort w/o carbs but I just haven’t found that to be the case. If you start over w/ Sweet Spot I and ramp up while low carb/fasted… you’ll adapt as you go & be ready for the build plans w/o sugar. Check out the “Art & Science of Low Carbohydrate Performance.” It’s an easy read and will answer a lot of your questions.

1 Like

I went/tried Keto 10 years ago. For a year or so. Quit it because I couldn’t stand the food choices anymore. And my racing really suffered even though I was mainly into MTB 12h races at that time. Still an intermittent sport,may be different for ultrarunning. Introduced carbs again and saw an immediate positive effect on so many different levels. Especially on how much training I could tolerate. Not just intensity.

These days I simply feed my workouts. Restdays/ easy days will see little carb intake, training days more. Depending on the workout(s). A simple balanced diet.

Despite my chronic carb intake I can easily ride many hours without any food. Getting through this is more mental than pyhsiological for me.

1 Like

I’ve been doing all my workouts fasted. I did a full round of SSB 1 & 2, build and specialty phases last year, and I’m just about to finish SSB Mid Volume 2 for my new season.

Basically, I’ll eat dinner (sometimes carb heavy, other times not so much), then jump on the trainer the following morning. I’ve found workouts quite difficult at times, but always managed to push through and complete them.

I’m unsure if I should stick to this, or maybe try adding in something pre-ride before sweet spot or above – I’m thinking English crumpets with maple syrup… Especially if I’m due to start a build phase in a week or two…

I prefer the idea of being ‘fat adapted’, but I also want to optimize performance. If eating some fairly simple carbs right before a workout helps me complete it, are there any disadvantages to this approach?

Ideally, you want the best of both - robust fat metabolism, but also train your body to use/process carbs when riding.

Training both of these can be in conflict. My plan this year is to do my base training endurance rides (4hrs or so) with no carbs. Then as the season goes on, gradually increase the intensity of these longer rides, and eat more carbs.

For my trainer sessions - 60-75 min VO2max and threshold sessions - I generally don’t eat any sugar before or during. But do make sure I’m appropriately fueled with good quality carbs 3+ hrs prior.

I usually do these in the evening, and could see them being tougher if I did them in the morning. But many people have posted on this forum that they can get through tough workouts in the morning if they fuel appropriately the night before.


Question? So I did Pierce yesterday (1 hour 15minutes) and only fueled for the first hour with electrolyte drink mix that was at 10 am. I was hoping to stay fasted for Dans the next morning but I felt terrible not eating all day and wanted something in my stomach before bed, so I ate a can of tuna which claims to have zero carbs at midnight. my ride will be at 10am with only a cup of black coffee. my question is? am I in a fasted state or just glycogen depleted?

Sorry I don’t have time to read every post and re-listen to every podcast on the subject and I often get distracted and forget my original question. I’m guessing I at least had a calorie restricted day. :slight_smile:

Thanks everyone!