The Science of Running question: Running long runs on low amounts of carbohydrates is good. To what extent should I follow this?

ElGuerroujFan wrote:

My question is how long before the long run should we eat? How long should we wait after the run to recover?

I would feel kind of nervous trying this, since I feel like you could pass out or suffer from a nutritional deficiency if you do this too many times. Hope some of you have experience with this!

Generations of runners in the UK have raced on Saturday, had a snack, had dinner at a normal time, and stayed out drinking beer, then made it to the club Sunday run on nothing more than a coffee and banged out a solid 12-15 miles. Your muscles can be full of glycogen from the day before, you don't need fuel too close to the run. Plus, there's the definite benefit of not needing to take a dump mid-run.

If you are a young runner training to improve your fat metabolism, or an old geezer trying to lose a few pounds, then run fasted or nearly-fasted. Apparently a strong coffee helps you burn fat a bit quicker for fuel.

Personally, if I'm setting off for a long run mid morning, I run much better and faster if I have a banana an hour before than if I am 100% fasted. That's only 100 calories, 10% of what the run will burn, but it seems to speed me up. I'm not sure more food that that would bring more benefits.

As for fasting afterwards: we know you absorb carbs and protein much more efficiently in the 'golden hour' after training. I've heard little or nothing about the benefits of this, but recovery matters. Maybe others here know more about this...

Here's one protocol:

https://www.outsideonline.com/health/running/training-advice/workouts/workout-of-the-week-depletion-double/

All the so-called science surrounding carb depletion seems kind of sketchy to me. Admittedly, I haven't delved all that deeply into it, so maybe I'm missing something. But the part that always gets me is the general vagueness of "you're training your body to metabolize fat better when you're short of glycogen", or something along those lines. Like, what part of your body exactly are you training? What mechanism are you influencing? What lasting, helpful physiological effects does carb depletion have on your body?

In the Outside magazine article that is linked, Matt Fitzgerald mentions training at altitude and training in the heat as established ways to change your physiology in ways that improve distance-running performance. Altitude training results in increased red blood cells; heat training results in increased blood volume. So far so good: assuming the science is correct, those methods at least seem plausible and easy to understand. But what does carb depletion actually "do"?

I guess the point I'd like to make is, you can't just decide to train to improve some facet of performance and have it automatically work. For instance, I would assume that you can't train your body to function well while dehydrated merely by going into your long runs in a dehydrated state. Because, other than maybe a slight psychological adaptation, what would be "trained"? And that's how I look at carb depletion.

I'm not saying it definitely doesn't work. Maybe it does. It just seems that the evidence is thin at best. Note the lack of specifics in Fitzgerald's description of the benefits of running on depleted carbs:

"It is generally believed that the main purpose of this practice is to increase the fat-burning capacity of the muscles, but most of the research on carb-restricted training has focused on a completely different benefit. That’s right: increased aerobic capacity.

What scientists have found is that muscle glycogen depletion (glycogen being the muscles’ preferred carbohydrate-derived energy source) is a major trigger of some of the physiological adaptations that enhance the body’s ability to use oxygen for muscle work. Normal training results in a degree of glycogen depletion, but carb-restricted training augments this stressor and the resulting benefits. The specific idea behind this practice is to start workouts at low muscle glycogen levels instead of merely finishing them there."

ElGuerroujFan wrote:

I have done some reading on The Science of Running book by Steve Magness. While there are a lot of important concepts which I now understand more, one stood out to me which was that long runs are supposed to be run on low carbohydrates to get the full benefit. As he suggests, mitochondrial change occurs when we are low on carbohydrates, and therefore we should not "chug down a Gatorade right after a long run".

A more important piece of advice from Magness is: Don't go there until you have to go there. A fasted long run isn't something you do as a teenager to work on your 5K time. It's where you go after you've maxed out regular long runs, and when you're focused on the marathon.

I've been on a high carb diet since 1974, and pretty much before that as well.

El G ate a high carb diet.

There was a 50 mile winner in the 1970s with a shirt that read "I'd rather eat worms than deplete."

I read an interview with Swedish marathon record holder Mustafa Mohammed recently and he said that most elites had quit doing long runs on low carbs. The cost was too big. You risk losing quality on the long run and the recovery is longer.

I wonder how much of the benefit is mental: training your brain to accept glycogen depletion. So teaching yourself that it's OK to let glycogen levels dip, you don't have to throttle back when they get low in the last miles of a marathon.

That would be pointless for anything shorter, of course, unless there's some physical benefit as well.

This is a complex area. I suggest looking for articles and papers by Louise Burke from Australia. She has conducted research on the area. Here is one to start with

https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP278928

As others have said, the science and evidence on this is fairly limited and inconclusive at the moment. There are examples of people doing their long runs with little to no fuel, you mentioned the Kenyan examples, another would be the current 24hr, 12hr and 100km record holder Aleksander Sorokin, who seems to do his long training runs with 500mls of electrolyte fluid and a banana, but he does eat every 20ish minutes in the big ultra marathon efforts. The electrolyte and one banana isn't something he seems to recommend, as far as I'm aware his only solid comment on it is that it 'works for him'.

Nutrition is very personal, I don't think there are really blanket rules that work for everyone. I'm a fell runner and I've got a couple of mates who are older blokes, one has a giant ziplock bag of cheese sandwiches in his bag on long efforts (2hrs+) and the other just fills up a 2 litre water bladder with pepsi/coke for long efforts. They're both in their late 50s so they've had years of messing about on the hills to figure what works best for them. I tend to start off fasted and then start fuelling after 30 mins, every 30 mins, if the run is going to be longer than 1.5 hours. Up to 1.5 hours I don't bother unless I need to get some extra stomach training in for an ultra, so it really just depends on what you're goals are, how your body reacts to different stimulus and what you're feeling on the day.

Man, you’re just a young kid, and not racing long distances yet. Wait til your body is fully matured and you move to the marathon before you start worrying about things like this.

Well, whether you like it or not, more muscle glycogen equals better recovery. So by all means, do as you like but what would have; better recovery or mithocondria adaptations? In my mind, one might get you injured if you're not careful so the questions seems easy.

Can't find the source but the norwegian scientifical paradigm evolves around train high, compete high according to my knowledge. Heard an leading expert in Norway saying this on a podcast recently. And we know Norway isn't exactly a endurance nation not to look to for scientific claims.