Attention All Dublin Marathon Runners

An insight into carbohydrate loading

Digest this blog like you do your post-run meals and you will be well-informed about the science behind carbohydrate loading in time for the big day.

Step one – Understand the Science.

When you run, your muscles require fuel to move.  This fuel is called Glycogen.  Glycogen is simply sugar stored with water in your muscle cells, and also your liver cells.  I can safely say that anyone reading this who has been training for months and eating well in preparation for the Dublin marathon will have bigger glycogen storing capacity in their muscles now compared to a time when you were not regularly training.  There is the potential to almost double the size of your glycogen stores with regular training and sufficient carbohydrate daily intake.  This is yet another added benefit to regular exercise, in that the more you do, the better your body becomes at doing it.

Carbohydrate loading is the topping up of these glycogen stores to the absolute max so that your muscles have a full tank of fuel on the day.  Why then is there the need for thousands and thousands of gel sachets available on the streets of Dublin come October 26th, because no human has a tank big enough to get around the 26.2miles without adding some more fuel into the furnace.  So whether you’re a glass half empty or half full person, in this instance, make sure it’s completely full.

Step two – Pick your carbo-loading approach

Long Taper:

If going with this option, you will have already ticked off your longest training run, I hope! (My wife and I managed to squeeze our 20 miler in last Monday, after our own leaving party in Glasgow last weekend was larger than expected!).  Your running schedule will be shrinking every week leading up to the 26th of October.  (For anyone reading this who is unaware what is happening on the 26th of October, please type the ‘date’ followed by ‘Dublin’ followed by ‘pain’ into google to find out).  With this approach, you do not need to eat extra carbohydrates since you will be running less and so burning less calories as a result.  Stick with the 5-7 grams of carbohydrate per kilogram bodyweight per day formula.  See below for tables detailing what 5-7 grams/kg/day means for you.  This will ensure that your muscles fill up their glycogen stores, which will not be hugely depleted because of the tapering in training intensity.

6 Day Plan:

With this approach, you need to deplete your glycogen stores six days before the marathon.  You can achieve this by doing an intense session, not a slow long run, instead get in some quick sprints or intervals, lasting over 90 minutes.  Following this, the next three days would consist of a mixed diet containing 5-7 grams of carbohydrate/kg bodyweight/day along with tapered training.  From the 23rd of October, you would further reduce your training, or rest completely and increase your carbohydrate intake to 9grams/kg/day.

Rapid Loading:

This option is only advisable to those who have tried and tested it.  It involves continuing your training schedule without tapering.  Then perform an intense glycogen depleting exercise session 24 hours before the event.  Once finished the exercise session, the goal is to consume >3000 calories of carbohydrate within the same day.  Three thousand calories of carbs is equal to 750 grams.  Refer to the list below to see how much of your favourite foods you need to make up 50g of carbs.

Rapid loading would be an appropriate choice for someone who is doing the marathon and then needs to enter another endurance event soon after, or maybe for someone who did not lodge enough miles in the bank leading up to the marathon and so can’t afford to taper off.  Otherwise picking between the three options can simply be a matter of what works best for you.

Table showing what 5-7 g of carbohydrate per kilogram bodyweight per day looks like for your bodyweight.


(multiply stones by 6.355)

8 50.8 254 – 356g
9 57.2 286 – 400g
10 63.5 318 – 445g
11 69.9 350 – 490g
12 76.2 381 – 533g
13 82.6 413 – 578g
14 88.9 445 – 622g
15 95.2 476 – 666g
16 101.6 508 – 711g
17 108 540 – 756g
18 114.3 571 – 800g
19 120.7 604 – 845g


(Remember:  It takes REGULAR TRAINING as well as eating a lot of carbohydrate to increase your glycogen storage capacity)



Weetabix                                 4 biscuits

Rice Krispies/Cornflakes        1 large bowl

Muesli                                     1-1.5 cups

Porridge-made with milk        1.5 cups

Porridge-made with water      2.5 cups

White bread                            4 slices

McCambridge brown bread    3 slices

Bread Rolls                             1 large (baguette style) or 2 medium

Pitta                                         2 small pittas

Cereal bar                                refer to packaging

Chocolate biscuits                   5 – 6

Jaffa cakes                              6

Muffin                                     1 large or 2 medium

Scones                                     3 medium

Croissant                                 2 medium

Rice, boiled                             1 cup

Pasta/Noodles, cooked           1 cup of raw pasta

Spaghetti                                 1 cup of raw spaghetti



Fruit, canned in syrup             1.3 cups

Fresh fruit salad                      2.5 cups

Bananas                                   2 medium – large

Mango/Pear/Grapefruit           2 – 3

Orange/Apple                          3 – 4

Nectarine/Apricot                   12

Grapes                                     2 cups

Melon                                      6 cups

Strawberries                            12 cups

Raisins                                     2 tablespoons

Dried apricots                         22 halves



Potatoes                                  2 – 3 medium

Mashed Potato                        7 heaped tablespoons

Sweetcorn, canned                  1.2 cups

Carrots                                    5 medium

Green beans                            14 cups

Baked beans                            ¾ large (420g) tin

Lentils/kidney beans               2 cups

Peas                                         5 cups



Milk (full-fat/low-fat)            1 litre

Custard                                   1.3 cups

Strawberry yoghurt                 2½ pots

Diet Yogurt                             5 pots

Mullerice                                 1¼ pots

Vanilla ice-cream                    1.5 cups



Table sugar                              50g

Jam                                          3 Tablespoons

Honey                                     3 Tablespoons

Mars bar                                  1¼ bars

Cadburys ‘Dairy milk’ bar        1.5 bars

(ie – 8 squares chocolate type bar)



Goodfellas Pizza (dinner-plate size):

Thin base                     ⅔ pizza

Thick base                   ⅓ pizza

Hamburgers                             1.3 Big Macs

Lasagne                                   400g serving

Fried rice                                 1.3 cups (1 large serving)

Brown rice                              1.3 cups

McDonnells Supernoodles      ‘Almost’ one packet (One packet provides 60g carbs).



Orange juice                            500mls

Apple juice                              500mls

Cranberry juice                        500mls

Coca Cola/Other soft drink    500mls

(Note: diet soft drinks contain no carbohydrate)

Powerade                                800 mls (or 1½ ‘Volvic bottles’)

Diluted cordial drinks             800mls

Finally, just a few general tips on carb-loading.  I am trying to make more of an effort to keep my blogs short and sweet.  No pun intended!

When it comes to the day before the event, or the 28th of October in this case, the old school of thought was to eat a huge portion of pasta before bed.  This advice has changed over the years, since a large volume of carbs last thing at night may result in heavy, sluggish legs next morning, due to the water retention with high glycogen loading.  Instead, make your lunch sitting on the 28th your pasta party and then have a lighter dinner that evening.

As for what to eat on the morning of the race, that is very much an individual choice and has a lot to do with what foods you are comfortable eating.  Ideally a complex carbohydrate cereal such as porridge or weetabix would work, rather than a fry-up.  Personally, I’m relied on my trusty Lidl wheat bixies to give me the edge on the day two years ago!  A study shows 85% of people say they are tasty!

Remember that even though your glycogen stores will be at their peak capacity, they will deplete during the run.  Typically glycogen stores will provide our muscles with fuel for 60-90 minutes of activity that is moderate to high intensity.  Be sure to top up with gels or low carbohydrate drinks such as Lucozade sport beofre this time has elapsed and continue to do so every hour as per directions on the gel packets.

The reason why Lucozade sport and other sports drinks are advantageous is because they contain the ideal amount of fluid, carbohydrates and electrolytes (sodium, potassium, magnesium).  This allows the body to rapidly reabsorb it from the stomach into the blood to be used by the muscles, meaning you feel the effects very soon after drinking.  The main disadvantage is their price.  There is a way around that, make your own!  Add 250mls of fruit juice to 750mls of water with a pinch of salt and a good shake.

For any runners watching their weight, expect to put on between two and four pounds with carbohydrate loading in the last week.  This is because for every gram of glycogen the body also stores three grams of water.

Try to continue to include an adequate amount of protein in your diet when increasing your carbohydrate intake.  Protein is essential in the repair of our muscles following training. An adequate daily intake would be between 0.75 – 1 gram of protein per kilogram of bodyweight per day.

Step three  –

Complete those 33,000 steps with power and pride, cross the line to bask in the glory of completing the marathon, becoming one of the world’s 1% of people to have finished the famous 26.2 mile race.

Hope you have enjoyed reading this blog and have found it helpful for your pre-race preparation.  Good luck to each and every one of you on the day.

John Phelan

Chartered Physiotherapist and Nutritionist

Leave a Reply

Your email address will not be published. Required fields are marked *