Carb Overloading

Posted: 23rd May 2013 by mockjogger in Race Preparation, Training Plan


Before running my first race in April this year, I enthusiastically embraced the practice of carb loading. My execution involved a pizza lunch and a pasta dinner the day before the race. I felt good, covered the distance in a time I thought was impossible, and put some of the result down to efficient eating.

So a week before my second race I thought I would do even better, and up my carb intake over a longer period. I found myself in Pizza Hut with family and a 2 for 1 voucher and started then. Next day I headed off on a short family holiday. The weather turned out to be great. In Scotland, you can’t miss opportunities like that, so I found myself setting up a beach barbecue with rib-eye steak, bread, Grolsch beer and more bread (a combination that really shouldn’t work but does). The following day, the weather held up and I strolled across to the Meadows in Edinburgh for another barbecue, together with almost everyone else in the city.

apeIt was during a magical post-barbecue chocolate moment that a thought suddenly struck me – am I using carb loading as a front for binge eating? I thought I better do some quick research, otherwise I was in danger of wobbling around the Edinburgh 10K EMF course on Saturday in an impression of Mr Blobby dressed as a gorilla.

I now understand the following important points:

    1. The body stores energy in the form of glycogen and fat.

    2. During a run the body accesses energy from glycogen stores first

    3. When the glycogen stores are empty (as in, she can’t take any more, Captain), the body looks for fat.

    4. The wall experienced by many during a marathon (although I can’t verify this as I haven’t run further than a half marathon yet) occurs when the body runs out of glycogen and switches to burning fat, as burning fat is less efficient and takes some time to kick in.

    5. Carb loading is simply the mechanism to charge up the glycogen stores as much as possible before a race.

Barbecue on the banks of Loch Coil

Barbecue on the banks of Loch Coil on 20 May

It turns out that there are several generic carb loading strategies. The most common approach is to fuel up with carbohydrate-based food in the 2 days leading up to a race. The best time to fuel up is after a taper run, when the body is ready for it. Pre-race dinner should be carb-based but not excessive.

As for distance, by most accounts, charged-up glycogen stores will last around 16-20 miles. Carb loading is generally recommended as part of an overall race plan for a half marathon or more. There is some debate about whether it is worthwhile for a half but the balance of opinion is in favour. For shorter distances, e.g. my 10K on Saturday, the consensus is clear – there is no benefit to be obtained from carb loading and I should just eat normally.

So where does that leave me? I went out for my last training run before the race yesterday, after a 3 day break, and felt laboured. I’ve reverted back to my normal diet and don’t plan on eating more than my usual intake from now until the race. Lets see how that goes.

  1. I don’t even carb load for my 6+ mile runs, and until I read this post, didn’t even consider it. Just good food full of fuel and drink plenty of water tomorrow all day long, just in case Saturday decideds to be sunny and hot!

    Good luck!

    • mockjogger says:

      Thanks Danielle! The race is off at 9am on the Saturday, and I’ll be sipping away on some SIS electrolyte lemon / lime + water as I walk to the start. The forecast is “partly sunny” and I’m hoping to be in the “partly” bit. It’s my second race and I’m looking forward to it.