Thursday Training Tip : How to carbo load for a marathon

It’s marathon week for me so as I’ve turned a more focussed eye on my pre-race nutrition I thought I would share what I’ve learnt over the last few marathons.

Now, one of the very common questions I see around the interweb about carbo loading is:

Can a carbo-load prevent hitting the wall?

In all honesty, probably not. But it will prolong the time before you hit the wall and can even lessen its effect if you hit the wall. The reason is that for almost all marathoners the energy deficit between stored energy and that required to complete the race is so great that a carbo load can’t hope to make up the difference. Your body primarily uses glycogen (what carbohydrate converts to) for energy. When you deplete your glycogen stores, the body relies on metabolising fat (a much slower source of energy) and your pace drops dramatically. Couple this with dehydration and an elevated core temperature from the exertion and *boom*, it can feel like someone built a 10ft high masonry fence across the course.

However, optimising your energy levels before the start of the race, coupled with good in-race fuelling, will certainly increase the time before you reach ‘energy-deficit’ – that point when the wall starts looming in the distance – and can help minimise its impact if you do hit it.


0007 – Licensed to eat

James Bond took his carbo-load too far...

James Bond took his carbo-load too far…

Image Credit

Despite what a lot of people think, and most of us hope, carbo-loading for endurance events like half and full marathons isn’t a licence to gorge on pasta, fizzy drinks and sugary cereal. Carbo-loading is an important part of race preparation, and should receive the same level of focus as your physical and mental preparation.

Firstly, if you’re about to start your carbo-load and you’re still running, STOP RUNNING! Most people follow a taper plan before a marathon, but some then freak out in the last few days and think if they don’t run they’ll lose their edge. This is simply not true. The repair and fuelling of your muscles you will be able to achieve in the last few days will help to deliver you to the starting line in the best possible condition to race. Your likely marathon performance was already set 3-4 weeks before the race, running lots right up to the event will hinder, not help.

Ready to load? Here are my 8 tips to help you get the most out of your carbo-loading:

Save the ‘loading’ for later:

If you are tapering properly, keeping your same healthy training diet during the two weeks before the marathon will yield a natural carbo-load as your energy expenditure drops. As the intensity of your sessions drops, those extra calories will manifest themselves as glycogen in your body. However, it is important that you eat carbs for energy, not fat. Carbs will convert to glycogen, fat doesn’t.


Keep your ‘load’ close to the race:

It’s the last 72-48 hours before the race that you need to start ‘loading’. Doing it beforehand or over several days won’t top your glycogen levels up even more, and can in fact leave you sluggish as your body struggles to deal with the massive carb intake (or worse, decides you’re now living the life of plenty and starts storing it as fat).


Eat what you know:

Don’t drastically change your diet for the load – doing so can lead to stomach upsets. Start to move your diet towards your ‘load foods’ in the two weeks before the race by slowly cutting out the things you won’t be eating. Like pizza, in my case at least…
Try to stick to unprocessed foods if you can, the nutrients are unlikely to have been lost in the processing stage and will be better for you. Pasta, rice, wholemeal breads, oats, beans, lentils and beans are good sources for your extra carbs.

Pasta is a usual favourite for runners when carbo loading

Pasta is a usual favourite for runners when carbo loading

Image Credit

Water, water, water:

Drink lots of water! For every gram of carbohydrate stored as glycogen, your body needs to store 3 grams of water. If you weigh yourself regularly then expect your weight to jump up about 2kg if you’ve loaded properly. TMI warning – Make sure you’re producing a good volume of urine every 2-4 hours (that’s about 5-7 trips to the loo a day), and that it is pale yellow in colour. If it looks like pure water, it is, and you should reduce your water intake.

3 days to go – It’s ‘load’ time:

A 70kg runner needs about 350 – 490 grams of carbohydrates a day (5-7g per kg of bodyweight) making up about 60% of their total calorie intake when training. In the load period 72-48 hours out from the race, increase this intake to 8-10g per kg of bodyweight – our 70kg runner is now looking to intake 560-700g of carbohydrate per day and take 75-85% of calorie intake as carbs.

This is hard work as you will be eating more than usual, however it will be easier and better for you to add meals into your day instead of making your meals larger. 5 small meals is a lot more palatable than 3 massive meals and will also help keep your sugar levels from bouncing around too much. Your partner might thank you too, smoothing out your sugar levels will help minimise mood swings, one of the usual side effects of the ‘taper crazies’.

Also, supplement your food-based carb intake with carbs from liquid as well. Sports drinks are best, try drinking 1-1.5 litres of your favourite sports drink to help ‘top up’ between meals, but you can use fruit juice and small amounts of caffeine-free fizzy drinks as well. But don’t stop drinking water. Just gauge your hydration levels from your urination amount and colour.


Sports drinks come in all sorts of types and flavours, just make sure they are isotonic so they contain the right balance of minerals and salts


Here’s an example of what to eat during your ‘loading’ phase (courtesy of the Australian Institute of Sport)

Breakfast 3 cups of low-fibre breakfast cereal with 1 1/2 cups of reduced fat milk
1 medium banana
250ml orange juice
Snack toasted muffin with honey
500ml sports drink
Lunch 2 sandwiches (4 slices of bread) with filling as desired
200g tub of low-fat fruit yoghurt
375ml can of soft drink
Snack banana smoothie made with low-fat milk, banana and honey
cereal bar
Dinner 1 cup of pasta sauce with 2 cups of cooked pasta
3 slices of garlic bread
2 glasses of cordial
Late Snack toasted muffin and jam
500ml sports drink

Tomorrow is Race Day:

On the day before the race make sure 85-95% of your energy intake is carbs. Try to eat dinner early, ideally you want to be finished eating 12 hours before the race start so you have time to digest and get the carbs to your muscles (and your food through your digestive tract). Drink a sports drink before bed, and maybe add a small snack like a sports bar, but definitely not anything heavy.

Race Day:

Start eating 3-4 hours before the race starts, trying to get about 150 calories of carbohydrate in. Don’t overeat! You’ve already loaded your body with glycogen, the breakfast is just to replace the calories lost from your sleep. As you make your way to the race, make sure to be drinking sports drink to ensure optimum hydration and ‘brim your tank’ with energy. Tip: if you’ve got an early race start, get up, eat, then go back to bed. But be sure to set your alarm again! Twice…

During the race:

OK, this isn’t technically carb ‘loading’, however the energy deficit I discussed before means that you need to keep up your energy intake during the race to reduce the energy deficit and the impact of the wall if you hit it.

Gels, sports drink, candy, flat coke and bananas are good sources. Again, don’t gorge. If you’re reasonably fit (you should be, you’re running a marathon!), your body can handle a maximum of about 380 calories per hour when running. Any more than that and you run the risk of a GI upset and a frantic search for a porta-potty. If you eat 1.5 gels (one every 45 minutes) and drink half a bottle of sports drink you’ll be around 300 calories per hour. Add half a banana and you’re near to the limit. Again, try to even out your intake. Don’t get to an aid station and squeeze a gel, eat a banana and then gulp a sports drink all at the same time. At best you’ll give yourself a stitch but at worse, well, better hope there is a porta-potty nearby…


I hope with these tips you can master the carbo-load and give yourself the best chance of avoiding or minimising the effects of the wall. Now, where did I leave the pasta sauce? It’s time to start my carbo-load!

Happy running everyone!


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About getgoing-getrunning

Hi, I’m Bernie and I’m a just guy who writes about the things which get me going and get me running, even though my running is never going to result in me standing on a podium!

Posted on April 3, 2014, in Blog, Marathon de Paris, Marathon Training, Nutrition for Runners, Training Tips and tagged , , , , . Bookmark the permalink. 12 Comments.

  1. How could you do that to Daniel Craig? I may never forgive you!

  2. Great info Brenie. I probably won’t tuna marathon before December, but I will bookmark this post for when I do!!!

  3. Nice! Good tips! Too often everyone just overloads on pasta the night before the race. They need to learn!

  4. That was really helpful Bernie. Especially the bit about how much and what to eat during a race (this is an area that I have yet to get right). I’m going to bookmark this. Oh and all the very best for the Marathon as always 🙂

  5. Great post Bernie. The point you make well, which I think a lot of people get miss is the importance of energy drinks. It is nigh on impossible to consume 750g of carbs as solid food in a day (42 slices of granary bread!!!). Energy drinks are an essential part of the load and help with hydration.

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