Thursday Training Tip : Carbo loading for endurance races

Carbohydrate loading for marathons and ultras

This weekend is my first Ultra so for this week’s Thursday Training Tip I’ve decided to re-look at carbo loading as a way to maximise race performance. Carbo-loading is an important part of race preparation, and in the days leading up to your race should receive the same level of focus as your physical and mental preparation. Optimising your energy levels before the start of the race, coupled with good in-race fuelling, will increase the time before you reach ‘energy-deficit’ – that point when the fabled ‘wall’ starts looming.

Firstly, if you’re about to start your carbo-load and you’re still running, STOP RUNNING! Everyone should be following a taper plan before an endurance race, 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 race 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:

1) Don’t jump the start:

If you are tapering properly, keeping your same healthy training diet during the two weeks before your race 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…]

2) Keep your carbo 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 high-life and starts storing it as fat).

3) Eat what you know:

Don’t drastically change your diet for the carbo 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.  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

4) 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.

5) Three 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

6) 24 hours to go:

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.

 7) It’s Race Day:

Start eating 3-4 hours before the race starts, trying to get about 150 calories of carbohydrate in if you’re marathoning. If you’re doing an Ultra then the energy expenditure is gong to be massive and a proper breakfast 4-5 hours before the face of 300 or more calories is a good idea. Just keep it light – 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…

8) 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. If you’re ultra running then items with more substance like Clif Bars are a good idea. Over the time period of an ultra you will get hungry. Properly hungry! Something like a Clif Bar will give you a mix of fast and slow release energy and a bit of volume in your stomach. Again, don’t gorge. If you’re reasonably fit (you should be, you’re running a marathon/ultra!), 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. Ultra runners often eat every 30 minutes, but a little less each time, to even out their intake. Avoid getting to an aid station, taking a walk break and squeezing a gel, eating a banana, half a Clif Bar and then some gatorade to wash it down! 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 having the energy you need for your race. Speaking of which – my spaghetti carbonara is ready…

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 September 11, 2014, in Blog, Marathon Training, Nutrition for Runners, Thames Path Challenge 50k, Training Tips, Ultra Training and tagged , , . Bookmark the permalink. Comments Off on Thursday Training Tip : Carbo loading for endurance races.

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