Eating to Fuel Endurance Training and Long Distance Races
A subject I am often asked about is ‘what is the best food to eat for marathon training, ultra-marathon running, Ironman training’ and so on. I have lots of friends involved in endurance sport, and I have a reasonable amount of experience myself, and there is a lot of confusion and misunderstanding about fuel for endurance sport. Personally, I have been in long distance endurance events with far more experienced runners than myself and seen them fail and drop out because they ‘got it wrong’ with their fuel, yet in my own experience, such problems are entirely avoidable most of the time.
This post will explain:
- Why complex carbs are not the best fuel for endurance races
- Why complex carbs are not required in great quantities pre-race (carb loading)
- Why gels and bars are not the best fuel to consume during a race
- How to be ‘a fat burner’, not ‘a sugar burner’
- Understand how to unlock thousands of calories of energy for long races
First of all, I think you might like to start by reading my ‘intro post’ on running: https://mothernaturesdiet.me/2013/08/26/838/ It’s quite short and simple, and briefly explains why I prefer trail running to road running.
I was recently asked if I had experienced any problems when I switched from a ‘typical’ runners diet (high in complex carbs) to a low-carb ‘paleo style’ diet – did I then find myself getting close to a ‘bonk’ when training or racing? Now you might ask ‘what is a bonk?’ While some may think it sounds like fun, sadly it’s not that kind of a ‘bonk’!! Endurance athletes have several expressions for this, you will often hear marathon runners talk about ‘hitting the wall’ or you may have heard some endurance runners talk about how they “got X miles in then crashed” or “I blew up at X miles”. Bonk, or ‘hit the wall’ or ‘crash, or ‘blew up’ all mean the same thing, it’s when your body runs out of energy completely, your blood sugar level hits ’empty’ and you get all dizzy and have nothing left inside you. This is when endurance athletes are often forced to drop out of a race, and they have to declare ‘DNF’ = Did Not Finish, the last thing any of us ever want to see on the Race Results Sheet! All that effort, training and preparation, the excitement, the build-up, the anticipation, ending in a DNF is soul destroying.
Most (a generalisation, yes) endurance athletes use these sports gels and energy bars to keep themselves fuelled during long distance events. The majority of sports gels are basically just a blast of sugar, a little water, some minerals and often a dash of stimulant, such as caffeine. I could write an extensive post about gels. We could talk about how the minerals are essential to replace lost electrolytes, without which you could face painful muscle cramps in your legs, which can be agony, believe me. We could talk about the pros and cons of stimulants. We could talk about the artificial ingredients, and the healthier home-made alternatives. We could talk about how many athletes consume lots of these gels or energy bars then end up DNF on the side-lines of the race, vomiting with painful stomach cramps. But this post is about racing without gels, so we will leave all that for another day.
First, the science bit
In order to understand how to best fuel our bodies for long distance races, first we need to understand how our bodies metabolise sugar and the role of insulin in this process.
Sorry to send you off there to read that little bit of extra background reading, it just seemed easier to give you that link, rather than re-write all of that here again in this post.
In a nutshell, when your body has glucose floating around in the blood, you will also have insulin in your blood too. Keeping the science to a minimum now, and talking in very basic terms, the role of insulin (which is a hormone) is to file nutrients away where they belong. Insulin does many things, and helps to send various nutrients where they are supposed to go, but for the purposes of this thread, the main role of insulin is to clear those excess blood sugars (glucose) out of your blood. It will help push those sugars into your muscles if they need it (which obviously they do during a marathon or Ironman) and then it will take any excess glucose and push it into fat cells for storage.
So in that link above, you read about how insulin sets up your body chemistry in a way that creates a ‘one way door’ into your fat cells. When insulin is present in the blood, in reaction to the presence of glucose, those ‘one way doors’ into fat cells are open for glucose (energy) to flow IN not OUT.
Eating on the run
If you are eating carbs (such as gels and energy bars) during long training sessions or on actual races, then the sugar quickly reaches your blood, insulin is triggered, and your muscles start sucking up the glucose. Essentially, that is all good, your muscles need the fuel. Fuel = happy muscles. Those muscles will keep going until the build-up of lactic acid ‘blocks up’ the muscles so completely that they have no space left to take in further glucose, at which point you either need to stop, get a massage, rest, hydrate and then go again, or fatigue ends your race.
However, there is another side to this story. I see a lot of runners on marathons and ultra-marathons setting off with masses of gels at the ready. After the first hour or two has elapsed, they start taking a gel of a half of an energy bar roughly every 20 or 30 minutes, the idea being to keep fuelling the muscles. Eating those carbs constantly, means that insulin is pretty much constantly present in your blood. If insulin is constantly present, the one-way-door to your fat cells is permanently open for IN, not OUT. This means that your body can never access your fat reserves as a source of energy. There are tens of thousands of calories of energy available in body fat, even on a fairly lean person, and yet while fat cells are in ‘receive’ mode, not ‘give’ mode, those energy reserves remain totally unusable.
In order to access fat, your body chemistry needs to be set up to burn fat. The one-way door needs to be set to OUT, and they won’t happen in the presence of insulin.
If you are running on sugars, it’s a game to keep putting them in every 20 or 30 mins. As soon as you stop, 20 mins later = bonk. I believe that this is what marathon runners talk about as ‘hitting the wall’. It’s when they have burned up breakfast, sucked down their gels, and their blood sugar crashes and they hit ‘empty’. They feel wiped out and they just can’t go on.
Now, all that above is pretty solid science. The rest of this post is based somewhat more on my own ‘experiential learning’.
If your workouts are anything up to an hour or two, for most people, I guess healthy complex carbs are a perfectly good source of energy. You eat some food, you go burn it off. Personally it’s not really how I train, but if that’s your style, then I guess that works for you. I believe that sustained aerobic exercise (endurance running, triathlon, etc.) needs a much better source of slow-release fuel, and if you are trying to fuel serious workouts, like the 10 to 14 hours required for an Ironman or ultra-marathon, then trying to cram in enough food to fuel that will always be hard work. Rather than trying to eat all those calories in the hour before the race, or during the race, doesn’t it make much better sense to dig in to your existing energy reserves, your body fat? Your body carries tens of thousands of calories of fat, so that would be the perfect fuel, if you can train your body to access it, and set up your blood chemistry the right way.
To access that fat, you need to open those one-way doors to ‘OUT’ not ‘IN’. In order to achieve that, you want to ensure insulin is minimised, so the best way to achieve this is to not eat sugars/carbohydrates.
In my opinion, the reason most athletes bonk, crash, burn, blow up or hit the wall, is because they load up on a high-carb breakfast on race day, after a week of carb-loading, and after months of training with carbs providing their main source of fuel. Come the race, they get 2 or 3 hours into the event, and start sensing that energy levels are flagging, so they start popping gels. The blood-sugar cycle goes round and round…sugar in, sugar burn…sugar in, sugar burn…til they run out of gels and crash. (As an additional problem, many of the endurance runners I know, suffer from gastro-intestinal cramps caused by eating all that synthetic gel rubbish – in my opinion it’s not real food! I have tried gels and bars, and some are OK, but I found that if I had any more than 2 or 3, they started to make me feel a bit sick. Real food never has that effect on me.)
To me, it makes much more sense to ‘train your body’ to use fat as the primary source of fuel. I have run a dozen marathons, 3 ultra-marathons, cycled John O’Groats to Land’s End (the length of the UK, 983 miles in 9 days), and yet I have never ‘hit the wall’ once. I have run for 11.5 hours non-stop over mountains, and cycled for up to 13 hours per day, but never DNF and never ‘bonked’.
I ran my first two marathons (Barcelona and Paris) as ‘a sugar burner’, because that was about the time that I was still learning about low-carb eating, and I still had a mental belief that I needed to load up on complex carbs for a marathon. If my memory serves me well, I took gels with me for those marathons. Then I learned about all this stuff and shifted carbs out of my diet and my training improved, my times got faster, energy more stable, I lost weight, and started finishing marathons in 3:40, not 4:20, and finished feeling like I still ‘had some left in the tank’.
Becoming a fat burning machine
By living low-carb all the time, over a period of approximately three months (training every day, often running and cycling, but some weights too) my body ‘learned’ to be ‘a fat burner’. I wasn’t eating carbs every day, except lots of vegetables and some fruit, but my diet was high in natural whole foods, eggs, meat, fish and veggies, and when I exercised, within no time at all, any available blood sugar had burned off, and my body was familiar with dipping into my fat cells for energy. I think it takes a time to ‘learn’ this behaviour.
Your body adapts to things over time. Think about how people who weight train talk about ‘muscle memory’, saying that it is easier to build muscle you once had but lost, than to build new muscle the first time. It takes time to train the responses, to establish the preferred metabolic pathways. Just the way repeated aerobic exercise conditions your heart, lungs, legs and so on to endure more and work longer or harder or faster. The same way you don’t damage your pancreas the first ever time you eat a sugary snack, but decades of eating a high sugar diet eventually leads to type 2 diabetes. Again, just the way repeated anaerobic training with weight conditions responses such as increased strength, larger muscle mass and faster recovery. These are all examples of a ‘conditioned response’ in your body. And in the same way, I believe your metabolism can be trained to respond to a workload (in my opinion…as I said, I have not yet done all the research on this) and once you are used to low-carb living, and your body gets used to using fat as fuel, then it goes straight there every time. It becomes a conditioned response, a preferred metabolic pathway. A path well-trodden is easy to follow.
Once your body learns that carbs are not coming in all the time, it will stop ‘seeking’ them as fuel source #1, and learn to use calories released from fat cells. In my experience (and not everyone will be the same, remember that), the more my body got used to not eating carbs, the quicker and easier my fat cells turned on and start providing constant stable energy.
Now, here in 2014, and paleo diets are ‘all the rage’, I see loads of people eating low-carb about 70% of the time, then loading up on carbs for long weekend training runs and for events and races. I think problems occur when you are eating low-carb ‘half’ the time (meal times during the week) and then suddenly carb loading on the weekend and shoving carbs (gels and bars) in during long training sessions and races. I think your body chemistry gets ‘confused’, it isn’t sure whether you are a sugar burning athlete or a fat burning athlete.
So I think eating low-carb is the best way to go for endurance sport, low-carb all the time, including pre-race, race day and during a race or event. POST event, then carbs are fine, shove in a ton of carbs soon and refuel your exhausted muscles. Post-training you should eat good carbs, especially in that 20 minute window of opportunity when your muscles are still highly receptive (pumped) then gulp down some fruit juice, dried fruit, a recovery or weight-gain shake if that’s your thing, or some dark chocolate. After the event, your energy systems are no longer trying to access calories from fat cells, you are now resting, and you want lots of glucose in your blood and all the insulin you can get, to ram those exhausted muscles full of glucose to aid recovery. Listen, I do not advocate eating junk food or consuming alcohol, but in all honesty, if you just completed something epic like an Ironman…well, if you want pasts, beer and ice cream, you go for it, your body will swallow up any calories it can. But post-workout is the only time for sugary carbs, in my opinion. The rest of the time, I get my carbs from vegetables and fruit only.
I have run 12 hour ultra-marathons over mountains fuelled on scrambled eggs and veggies. I ran the Exmoor CTS marathon and came first in my age group (vets), after scrambled eggs and sausages for breakfast, and a steak dinner the night before. No carb loading, and I won the event at age 40 and over. My personal PB marathon was in Copenhagen in 2011, where I ran a marathon in 3:14:17 at age 40. I had eggs and stir-fried vegetables for breakfast in my hotel that day. So the carb overload is not required, in my experience. On these runs, I take no gels or bars. Up to about 4 hours, I don’t need anything but water. On longer runs, I will snack on whatever is available at the aid stations on long races. In the UK it tends to be fresh fruit, dark chocolate or (worst option) biscuits, and I’ll avoid the biscuits if I can, preferring oranges, bananas or dark choc. In France they usually have salty meats and cheeses, hot salty soup (very welcome on a snowy mountain top!) and other excellent offerings.
Being a fat burner and competing in endurance events on a low-carb diet is not new. If you want to learn more about it, try Stu Mittleman’s book “Slow Burn”. He has run thousands of miles as a low-carb ultra-athlete and his book explains it all far better than I do, and in much more detail. But of course, what works for one person may not work for another. We are all different…I experimented with low-carb/fat-burner/endurance sport and it worked well for me, but it may not work for you. You have to try it out and see how you get on. This a fundamental point of ALL nutrition advice and ALL ‘diets’ and eating plans. A system or solution that works for one person, will not work for another, because we are all different. So you can only try each thing, as I have done, to find what works best for you.