Saturday, April 13, 2013

Carb Loading and the Law of Small Numbers

I normally don’t eat a lot of carbs. On a typical day I’ll probably have less than 80g, occasionally maybe on a hard training day I’ll have up to 100-150g. The carb based food that I do eat are mostly fruits, veg, and some dairy but most of the foods I eat are fat, protein, and fibre based. Theres are a number of reasons why I eat low carb, and one of the major reasons is that since I’m Type1 Diabetic it helps control my blood sugars (Carb counting 101 : small amounts of carbs = small amounts of insulin. The bigger the dose of insulin needed, more chance of getting it wrong. Getting it wrong results in frequent low/high blood sugars. Both of which are VERY BAD). There are other reasons but I’ll save those for another day. Anyway, thats how I generally eat. However last weekend I had entered the National Duathlon Championships being held down the road in Ashford. It was a 10k Run / 40k Bike / 5K run and was going to be very competitive. Although the event was going to be reasonably long (I reckoned about 2.5 hours) none of the parts were all that long in themselves - meaning I’d be going fairly flat out most of the time. This is different from other endurance events like a full/half marathons, long bike spins etc. where you’ll be going at a lower intensity. Racing at sustained high intensity up around your anerobic threshold mean you’ll burn through stored muscle glycogen much faster than lower intensity sub-threshold racing. So I figured I should probably engage in some sort of pre-race carb loading in preparation.

I don’t subscribe to the traditional carb loading theory - eating 10g of carbs for each Kg of bodyweight the day before an event seems a bit ridiculous to me. Based on those figures that would mean I would need to be eating 700g of carbs the day before the event. Now since your muscles and liver combined can only store a total of somewhere between 400-500g of glycogen (which is what carbohydrates gets converted to in the body), and even if we assume that muscle and liver glycogen stores were completely empty (which they aren’t) then you definately don’t need anywhere near 700g of carbs ... and whatever doesn’t get converted and stored as glycogen gets turned to fat - not good. I was thinking more along the lines of 200-300g of carbs would be just fine. Even at that it was at least 3 times more than I’d normally eat in a day.

So I started off with a bowl of porridge pimped up with extra fruits and honey and took my usual ration of fast acting insulin. Post meal blood sugars were perfect, all good so far. But it went downhill from there. A snack of oatcakes mid morning resulted in a bad low around lunchtime - full on shakes and sweats needing a Lucozade to bring them back up. That was my planned lunchtime 3k leg stretcher run out the window. Potatoes for lunch and I reduced my ratio a little, and post meal blood sugars were perfect again. Quinoa for dinner and reduced my ratio even further, but 2 hours later another low - this time I needed a tonne of jellybeans to fix it. All these lows were making me tired too, not good prep for a race. I spent the rest of the evening worrying about why this was happening and before heading to bed set an alarm to wake me to check my blood sugars. 3am wake ups are not ideal before a race. 

Next morning things didn't get much better. The race wasn’t until 12:00 so I could have a breakfast around 8 - meaning any active insulin bolus would be done by 12. A banana smoothie seemed like a good option - some carbs but not too much to need a big insulin bolus so should be safe ... wrong again. 2 hours after breakfast just as I was getting in the car to leave - another low. Had to correct again with Lucozade but its definitely not what you need a couple of hours before a race.

All in all it was a hugely frustrating experience, and its actually the second time that carb loading has been problematic for me.  It brings me back to one of the reasons I eat low carb in the first place. In his book ‘The Diabetes Solution’, Dr. Richard Bernstein talks about ‘The Law of Small Numbers - Big inputs make big mistakes; small inputs make small mistakes’. How is this compatible with carb loading ... even low level carb loading. I makes me wonder if there is some better approach ...

Heres what the blood sugar rollercoaster looked like:

BG = Blood Glucose

08:00 BG 4.2 / 100g Carbs (Porridge, Banana, Raisins, Honey) / 7.5 Units Novorapid
10:30 BG 5.8 / 20g Carbs CP (Oat Biscuits) / 1.5 Units Novorapid
12:00 BG 3.2 / 15g Carbs (Lucozade)
13:15  45g Carbs (Potatoes) / 3 Units Novorapid
16:15 BG 5.1
19:30 BG 5.4 /  60g Carbs (Quinoa) / 3 Units Novorapid
20:30 BG 6.9
21:30 BG 3.2 20g Carbs (Jellybeans)
08:00 CP 4.5 (Smoothie - Banana, Berry, Coconut Milk, Honey) / 2 Units Novorapid
10:00 BG 3.8 / 15g Carbs (Lucozade)
12:00 BG 7.9

I'll try and get around to writing a race report from the duathlon soon ...