Carb Loading for Ironman

Introduction

There is a lot of nonsense written about Carb loading. This is a summary of an excellent article published by The Australian Institute of Sport – 

the original is available here: http://www.ausport.gov.au/ais/nutrition/factsheets/competition_and_training/carbohydrate_loading

What is it?

A dietary strategy to maximise muscle glycogen (carbohydrate) stores prior to endurance events. The modern technique is to combine a taper period (at least 1-4 days) with a high carbohydrate diet (7-12g/kg body weight/day).

What’s it worth to me?

Carb loading increases muscle glycogen by 1.5–2 times, and can result in a performance improvement of 2-3% over a given distance. That’s not far off knocking 1-2 minutes for every hour of exercise. Multiply that by 4-17 hours of long course triathlon, and it’s a significant chunk of time.

Who should carb load?

Anyone exercising at moderate to high intensity for more than 90 minutes is likely to benefit. Note that most studies on carb loading have been done on men – there is not much data for women. There is some suggestion that there are certain periods of the menstrual cycle that may limit the effectiveness of carb loading in women. But do it anyway, Ladies.

Common Mistakes

Many athletes fail to carb load properly or adequately. Here are some common issues:

1. You must taper while carb loading – continue exercising at a high intensity, and your body will continue to gobble up everything you throw at it, rather than storing additional energy. (See my article on tapering for further info on the importance of a proper taper before a race).
2. It is not an excuse to eat everything in sight. You must stick to high carb, low fat foods. Consuming high fat foods will make it difficult to eat enough carbohydrate, and may also result in gaining weight due to increased fat. You do not want to be carting a flabby arse around an Ironman.
3. You must eat enough carbohydrate. This is more difficult than it sounds, because it’s a lot of carb (see sample diet below). Carb/Calorie counter apps like myfitnesspal can help to keep track of your carb intake.
4. In order to consume enough carbohydrate, you will need to reduce high fibre foods, and increase compact carb sources such as sugar, cordial, soft drink, sports drink, jam, honey, jelly and tinned fruit. If you don’t do this, you risk stomach upset, or struggling to eat enough as fibre increases food bulk and the feeling of fullness.
5. You will gain weight. Possibly even 2kg! Don’t worry about this (as long as you’re not doing (2) above) – it is all glycogen and water, and will rapidly disappear on race day as your hungry muscles tuck into all that extra energy goodness.

Sample Diet

The following diet plan (from the AIS) is suitable for a 70kg athlete wishing to carb load. It provides around 14,800 kJ, 630 g carbohydrate (this is 9g/kg carb), 125 g protein and 60g fat per day.

Be amazed – it’s a lot of food!

(Easy sums: Multiply your body weight in kg by 10. This gives you a rough estimate of the grams of carb you need each day. Use myfitnesspal to keep track of your carb intake.)