One thing I notice riding with an endurance-focussed club is that I need more, and more frequent, feeding than many of the more experienced riders. As I start to think about longer days (e.g. 400km) and consecutive days with a few hundred km each, I've started to wonder if fasted training will help. This would seem like a good time of year to start as I'm unlikely to do more than a few 200s before the weather improves, then I'll want to seize the chance to get the longer stuff in.

I'm not trying to lose weight, but to be able to make better/earlier use of my fat reserves.

Recent cycling literature seems to be in favour of fasted training in the context of performance, but says little about endurance. There's general agreement that this is a fairly low intensity training ride but will take some recovery.

The consensus appears to be that a 45-90 minute fasted session once a week is beneficial, and that's something I could build in to an extended commute. But does this hold true when the focus is on endurance rather than weight loss? Or do I need longer fasted rides? There are suggestions of a small calorie intake after about 45-60 minutes, or a little protein intake earlier in the ride. Does this change if the goal is endurance?

  • I saw a related question recently, so I'll try to track it down and link it. It's a few years old and a lot of work seems to have been done since then, plus my goal is different.
    – Chris H
    Commented Dec 12, 2018 at 8:26
  • Related performance/weight-loss question from a few years ago: Training fasted: just about weight loss?. Also related: Improving metabolic efficiency. The latter, which I hadn't seen before, is in many ways more relevant.
    – Chris H
    Commented Dec 12, 2018 at 9:33
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    @Michael this type of training is even used by professional athletes at some points of the season. There is a quote out there from Carlos Sastre's coach that he used to go on a 5 hour endurance ride with 1 energy bar, eating half at the two hour mark, and the other half only if he felt he needed it. For sessions targeting hard intervals you are absolutely correct though, its best to fully fuel and get the maximum power out.
    – Andy P
    Commented Dec 13, 2018 at 10:18
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    @gschenk I think so. it's hard to tell for sure, because I was also concentrating on keeping the nutrition up on the really long ones and generally doing enough fairly long (200km) rides to count as training for the big stuff. I do think (especially at my peak fitness before my crash last year) that need for food became less urgent, i.e. my power output didn't drop so much when in need of a feed so I had more warning/more resilience. Now I'm finally back in work after lockdown I'll have to start the fasted rides again
    – Chris H
    Commented Oct 13, 2020 at 12:18
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    ... in early lockdown I was often going out for local evening loops of 80-90km. They were doable with no food at all, but much any hills at the end were easier with a little something after 40-50km
    – Chris H
    Commented Oct 13, 2020 at 12:21

3 Answers 3


I'll preface this answer by saying i don't have any formal qualifications or education to answer this, but it is an area I'm particularly interested in, and have spent a lot of time reading about (and trying out in practice).

With the above out of the way, the short answer to your question is yes.

In fact, the primary reason to be undertaking this type of training is for endurance/performance reasons rather than weight loss.

Your body is perfectly able to burn both carbs (either stored glycogen, or from recent intake), or fat. Burning carbs is easier, therefore, as you increase the intensity of exercise the proportion of carbs that are burnt is higher. Fasted training is about teaching the body that carbs aren't needed, and that fat should be its preferred fuel source at low intensity. By burning fat for energy, we are preserving our stored glycogen (and therefore energy levels) for longer. By starting off in a low glycogen state, and not providing any more carbs, we accelerate this learning process, and very much replicates the latter portion of a long ride when our glycogen stores are getting depleted.

I experimented with this type of training (and continue to use it) with great success during 2017 as an attempt to improve my endurance before undertaking the NC500 route in Scotland.

You need to be disciplined to get the most out it, and stick to HR/PZ2/3. It can be very dull, especially if you aren't used to it, and requires some advance planning to avoid prolonged steep climbs. For your example of commuting to work, this would mean no traffic light sprints etc.

For me, after trial and error, I found this was more convenient to achieve by 'low fuelling' rather than dedicated fasted rides. I would do my two interval sessions each week fully fuelled to get best quality. I would do shorter endurance rides (up to 2hrs) on only water. And for longer endurance rides I would ride the first hour on water alone, and then take half my usual carb intake for the remainder of the ride.

The process is very much like bringing yourself to the edge of a bonk in a slow controlled manner, without ever actually bonking. For this reason, i'd always recommend taking a couple of emergency gels on these rides just in case. It is often fairly unpleasant, with slightly increased breathing rate and a tired/lethargic feeling, but if things are going well, you should still feel you are applying the correct power to the pedals.

  • That sounds like you've done the sort of thinking I'm now doing. I can't avoid hills/lights completely but could plot a sensible route. I normally eat first thing so getting out even before that would be the key for me. I've also done a 3.5-hour ride, well-fed to start with but on just water (unusual for me) with the climbing near the start, and it wasn't too hard. In fact I hadn't really planned on it until I was over an hour in. I'm not organised enough to measure my calorie intake and halve it (partly as the effort expended over an hour can be very variable given varying riding conditions).
    – Chris H
    Commented Dec 12, 2018 at 14:13
  • Some of the endurance riders I have seen (and are successful) eat frequently. However, it seemed far more prevalent (and convenient) to fuel at less frequent intervals. If you are going to be doing rides or races that are long (6+ hours), it makes a lot of sense to train for this and adapt your body this way. If you are not planning to do much longer rides/races, I don't think it would be necessary. Commented Dec 12, 2018 at 16:25
  • @DeletedUser the rides I'd be training for are looking like about 20-24 hours, possibly with another 10 or so hours the next day. I've done a few rides over 300km in the last few months. As a baseline I ride a 200km at least once a month but if I can get some benefit from shorter training sessions that I can actually fit in, I'd like to do so, as 400km in a day is another step up (even without another 200km the next day)
    – Chris H
    Commented Dec 12, 2018 at 16:51
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    @DeletedUser It does actually have a utility even for shorter events/races. The more glycogen you can spare by burning fat earlier in the event, the more will be available, and the better you will perform towards the end. You are correct though, when doing longer rides, the ability to go further with less reliance on regular carb top-ups makes you much more versatile and robust, and much less likely to find yourself in a massive bonk.
    – Andy P
    Commented Dec 13, 2018 at 10:24
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    @Michael Fasted training is providing your body with a reason to adapt and increase the density of mitichondria (part of the cell responsible for fat oxidisation). Traditionally this is done with long endurance rides. The idea of fasted training is make shorter endurance rides replicate the later hours of a longer endurance ride. There are some scientific papers such as this one: ncbi.nlm.nih.gov/pmc/articles/PMC3253005 but as I said, i'm not qualified to analyse/comment on the results
    – Andy P
    Commented Dec 13, 2018 at 16:59

A tangential answer:

I did fasted commutes in 2019. These were 12 km rides, usually at maximum effort for the time of day.

In the beginning I rode once or twice a week. At the height of my cycling season I rode four to five days a week. On the return commute I was well fed and usually included 5 km to 10 km detours.

I did light carb loading about 8 hours before the ride, immediately before going to be. This I did not ride on a completely empty stomach.

In the beginning I regularly bonked at some point of the ride. Often it was at a tiny 5 m cusp about 8 km in or while shouldering the bike and climbing a 37 m stair.

First I did experience an improvement in recovery from the bonk, that is the effort I was capable of about five minutes later. This started from the second ride. After about two ten rides I recovered enough to sprint the last hill before my destination.

At this time the bonk became less sharp, eventually I felt that I'm running out of glycogen but did not have any of the systemic effects.

Finally I needed to do something unusually hard to notice anything at all. Eg running up the stairs, riding single trails, including a 20% climb, trying to keep up with roadies.

Side effects: I've been always so hungry after commuting. I ate plenty (and correctly nourishing) but stayed somewhat hungry. Less weight loss than one would expect for regular commuting.

In the evening I remained thirsty after drinking. I could still that thirst only with beer (non-alcoholic, wheat).

  • While this is only tangential, I never did a long ride in my life, it may provide two aspects that my help: (a) effects of fasted riding were noticeable very soon. (b) it is very easy to implement such training, better sleep at home and eat at work. (c) better recovery from bonks might be useful to increase robustness (feeding mistake, sudden power peak), if the riders metabolism might be quicker in switching to a ketogenic mode and 'soften the fall'. However, it might as well just not apply at all to an organism under the duress of an endurance ride.
    – gschenk
    Commented Oct 14, 2020 at 10:12

Yes, fasting sessions or training without breakfast is a great way to both extend your aerobic endurance capabilities and losing unnecessary fat.

Fasting rides improve your fat-burning metabolism, which makes your body utilize fats as fuel (on lower training zones), instead of carbs resulting in increased endurance. If you use fats as a primary source of energy, you'll be able to ride for many hours before exhaustion, because our body can store lots of fat. If you run o carbs on the other hand, you won't last that long because we can't store as much carbs in our body, therefore your endurance will fade very quickly.

It's important to remember that when doing fasting training, you should always keep your intensity low, just comfortable endurance pace is usually best. It's recommended to do at least twice a week fasting rides (but no longer than 2hours), at the preparation phase.

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    It could be helpful to explain why you can’t just burn through all your carbs then have your body switch to fat metabolism.
    – Rider_X
    Commented Oct 10, 2020 at 14:12
  • Also, as we asked in another answer of yours, can you disclose that your link is to your own site? Site rules.
    – Weiwen Ng
    Commented Dec 10, 2020 at 19:47
  • Yes it is site of mine Commented Jan 27, 2021 at 4:42

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