Maybe not "huge" but there's I believe, solid evidence of at least marginal benefit for fuelling workouts in your 3-5 hour range. Not just for the workout itself, but for the next one, if you're, for example, doing another 5 hour workout the next day on a weekend.

Fuelling during training is more about avoiding Relative Energy Deficiency in Sport (RED-S). It’s healthy to fast during occasional exercise but once you’re doing 2-3 sessions a day, every day, that’s a deep calorie hole to try and refill in a short period. Seems to be the limiter to training volume in low-impact sports. Not really about improving session performance - your muscle glycogen will burn no matter how much you fuel during.

I often do not take in calories with long brick sessions or long runs. I do when I race. I think you will find some differing opinions on this as you will with most things with exercise "science". I have tried to incoorperate more sessions where I do take in calories to help prevent trouble on race day and I have found I run better off the bike if I fuel more during a long bike/run brick. I have read about people purposely underfueling during long runs to help utilize alternative fueling pathways better, I recall when the Keto fad was really big people getting into purposely doing calorie deficit sessions with intention of trying to be more effeicient with energy production as has been pointed out its pretty much impossible to supply all your training/racing sessions without calorie deficit. I think the benefit/downside is debatable and I like to think maybe I get some benefit from the occasional no fueled session. I think there would be lots of variables that would be difficult to account for in most "studies" regarding the issue and likely many different theories as to the why's. I just find it annoying to have to find some fuel and carry it with me and I dislike gels, would much rather just head out the door and go.

I don't eat a lot while training either.

I even plan on using long runs and rides - to help maintain a healthy weight.

The last thing a bunch of overweight endurance athletes needs is a serious sports nutrition/junk food habit.

But trail is right here.

A little bit of food and electrolyte helps to radically improve the way I feel and perform on the last hour of training and the next day.

It's about more than REDS. There is reasonable evidence that carbohydrate consumption improves performance in high intensity efforts around an hour, or in moderate efforts of long than 2 hours. Before the body ever gets near the end of its glycogen reserves.

Not huge, but measurable improvements.

Yes of course, by increasing blood glucose availability - but we are talking about training. Of course in a race you should fuel throughout, as it's an ergogenic aid. The purpose of training is to stimulate adaptation, not maximise watts. For elites and many others, fuelling in submaximal training is simply part of a strategy to limit the energy deficit stress of the session. And nobody should be doing 'maximal' training.

Sure, there are theories about the various strategies. I'm of the mind that higher quality quality training is better than lower quality training . And avoid intentionally depriving myself of something, e.g. to "train your body to burn fat more efficiently", etc. . I could be proven wrong, not up to date on all the evidence.

How is your recovery from workouts? My thought would be that you are probably not "missing performance gains" during the workout if you don't fuel, but it's possible that the lack of fuel will make it harder for your body to recover fully after the session, which would then limit your ability to train effectively the next time you go out.

What does your overall training volume look like? I wouldn't make it to the end of the week if I wasn't fueling my sessions. Some pros are trying to take in 100g/carbs/hr when racing. Makes sense to train the gut & fuel training sessions. You might find that you're stronger in the sessions/don't have to eat as much afterwards. When I first got into tri I wasn't really fueling in training & it would be impossible to eat at times post session. Dealt with some reflux stuff. I do a lot better when my stomach isn't completely empty. You might also find that you feel better in training the next day. If you're doing a huge session that ends late in the day you might not be replacing what you lost even with a big meal & some snacking.

If you’re curious, isn’t it super easy to experiment?

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"FTP is a bit 2015, don't you think?" - Gustav Iden

My impression is that a lot of, possibly the majority of amateur cyclists and triathletes (not the ones that hang out on ST) never take anything during training.
For many of them the race is the first time they are getting any gels.

The purpose of training is to stimulate adaptation, not maximise watts.//

Really?? Where do you think the speed on race day comes from, the tooth fairy??

Surely he just meant that you shouldn't be trying to maximise your watts in training because that would mean you are actually "racing" during a training session. If you "push to the max" every training session, you'll burn out.

I just want to respond in case any young athletes read this thread, like I might have 15 years ago: There is an absolutely massive opportunity to improve your performance and health by fueling training adequately. Underfueling training is like detonating a physiological bomb of negative effects in the endocrine system in particular, with the hypothalamic-pituitary-gonadal axis suffering rapidly (sometimes in a single session). Lots of endurance athletes are going through the world feeling like garbage relative to their potential because they are messing up their sex hormones on long days, elevating cortisol unnecessarily, reducing resting metabolic rate as the body compensates for the severe stress, and generally making an uplifting stress into a destructive one.

The exciting thing is that fueling better is free speed! Across all endurance sports, there has been a much-needed realization: If you fuel enough in training, you put out more power while fatigued and recover faster, leading to higher power in racing. If you fuel enough in racing, that higher power you earned in training fades less as the event goes on. What many athletes used to think was a training or endurance limitation was actually a fueling limitation.

It's one of those classic situations where coaches and athletes need to get with it, or get out of the way, since getting anywhere close to individual potential requires fueling training. It's definitely possible to go long without fueling. It will just be slower (for all athletes) and contribute to worse health trajectories (for most athletes).

This is a huge opportunity, and that is so cool for your future!

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David Roche
Some Work, All Play podcast: https://podcasts.apple.com/...ll-play/id1521532868
Coaching: https://swaprunning.com/

^^^^This x Infinity..

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

You probably are not missing out on huge performance gains. I am a morning workout guy. I don't eat anything when I get up in the morning and as a rule of thumb if I am going less than 2 hours on the bike or less than 90 minutes on the run I don't eat anything. It has happened on multiple occasions when I will have a 12-15 mile run on Friday morning, get back late, am rushed to get to work, miss breakfast, and don't even remember that I haven't eaten anything all day until about 11AM.

Long slow workouts don't require a lot of refueling since your in the fat burning zone. When you get in trouble is when you show up for races with never having tested a refueling plan. At races you are at a higher intensity and but more glycogen and less fat so you can't go as long without refueling and risk bonking.

But what happens when you miss breakfast and are rushing to work after a decent session like that is that your body is in a big cortisol spike. The feeling is probably like you’re running on adrenaline and charging, pretty stressful but you just want to get stuff done.

Sometimes it is almost exhilarating to do this but for reasons explained wel in that long post above that can have a bad impact on your hormones and body and mood and recovery

I fuel my 2 hour sessions and then when I get home if I need to force breakfast I know I’ve started the recovery process earlier.

Sounds like you have a good plan and understanding what works for you so that’s good.

I reckon most of the high level riders I follow on YT have spoken about the goal is getting home and being kind of full so you don’t have a massive binge on junk and the recovery has started earlier. Chris Miller from the Nero show has old videos on this

Exactly. Anyone can sprint in a workout, or do a Zwift race. But should you? Besides, if adding carbs to your session makes it faster (by supporting glycolysis), how useful is that for long-course triathlon? Most age groupers should be trying to inhibit lactate production, not increase it. And yes, they are the same thing. Glucose has to first become lactate to make energy.

Why would you want to inhibit lactate production? Lactate is also fuel, it's used by the mitochondria to produce a large number of ATP

I personally see huge performance improvements when I fuel properly

Because every person has a similar limit to their glycogen stores and carb absorption during a race. The budget is slightly bigger in elites versus amateurs, but not by much. Average race pace needs to be within the cumulative budget. In age group Ironman, you would never be limited by your muscles’ ability to burn carbs.

Fuelling all sessions can be beneficial for other reasons (allows higher muscular force and speed of movement, quicker recovery, gut training), but definitely not “because watts”.

I don't eat when I train either. It's not like I want it that way. I lose appetite and don't want to eat anything except some water. I'm getting better though.
This is how I see:

If you eat and put some energy into your system, you can push harder and go further.
You will get stronger and faster after recovering from that training.

You should be able to tell the difference between training with the food and without the food.
Once you find that out, you will be more diligent to eat during training.

I don't know what a big cortisol spike is, but I know what it feels like when when I end a workout drained and I know what it feels like when I finish with something left in the tank. The days that I forget that I haven't eaten anything it is because I still have plenty left in the tank. You can't forget to eat when your body is running on low (it effects your hormones, body, mood, recovery) . I usually refuel 5-6 times throughout the day. I don't need to refuel during workouts too unless I have going more that about 90 minutes on the run and more than about 2 hours on the bike. :-)