Type 1 diabetes, endurance sport and the LCHF approach: Lewis’ marathon experience

Following on from Lewis’ post last week about life with type 1 diabetes and following a low carbohydrate high (healthy*) fat (LCHF) diet, here is a race report from the Auckland marathon:

I did my very first marathon (Auckland marathon) two weeks ago. As a reminder, I have type 1 diabetes, eating strictly LCHF for over a year. This is not a race report of the marathon, so much, but rather a detailed analysis of my blood sugar levels from before the gun went off to when I crossed the finish line.  I wear a Dexcom G4 Continual Glucose Monitor. I inject the sensor and carry a receiver with me. It gives me minute-by-minute live blood sugar readings, which I have downloaded for you. As a diabetic, my body is unable to regulate my sugar levels. If my sugar level is good, then the session is good.

The marathon itself, as my first, surprised me by how hard it was. Everyone says 30km gets tough but you have to really experience it to believe it. I could not believe how incredibly tough it was to keep going in the last 10km. My body was fine, but my brain was mush. I was trying to finish at 4hrs, and was on that pace until 30km, but then ended at 4:17. Definitely room to improve for next year. More physical training and certainly more mental toughness will help me last to the final 200 metres.

My sugar levels and my energy levels were excellent.

Interestingly, I tested my blood ketones (to test how “deep” in ketosis I am) before and after the race too, just to see what was going on. At the start, 05:30, my blood ketones were 0.5 mmol/L. This is pretty average for me. I really battle to get higher levels of ketones than that. After the race (11:00), my ketones were 1.5 mmol/l. This illustrated to me that my body is able to access fat burning when it needs it.

I have graphed it and the link below gives a good visual – however I’ve also provided it in detail below.

lewism

Background:

  1. Target range for blood sugar level is between 4mmol/l and 7mmol/l.
  2. During training/race, it is risky to have the sugar levels too low and if they drop below 4 mmol/l, then that causes all sorts of problems. At around 3mmol/l, you get reduced effort, an inability to push yourself, lethargy, and as it gets lower, I run the risk of passing out.
  3. Equally difficult for people with type 1 diabetes is the risk of the sugar level going too high. It is commonly understood that exercise reduces blood sugar level, but only if your blood sugar is below approximately 13mmol/l. Any higher than that, then exercise triggers a response that will increase the blood sugar level further. High blood sugars are extremely uncomfortable (not to mention dangerous), and exercise is not really possible.
  4. So during a race, my target range moves from between 4 – 7mmol/l to between 6 – 9mmol/l.

Race Day:

  1. Sugar levels were excellent during the night. Trending between 4mmol/l and 6mmol/l.
  2. There is something called the Dawn Effect, which causes everyone’s blood sugars to rise just at dawn. My Dawn Effect kicked off at 4am, and took my sugar (not caused by eating anything) from 4 to 7mmol/l.
  3. Before the race, my sugar level had stabilised. I take a cup of super-salty soup stock (taken from The Art and Science of Low Carb Living), and two coconut fat bombs (basically coconut oil, coconut butter sweetened with stevia). The fat bombs are to get in some good fuel from the coconut (which contain saturated fats) just before exercise – this is something you need to play around with, as everyone has a different tolerance level to coconut oil.
  4. You can see at the start of the race my sugar level then starts to rise again. This is a strange phenomenon that I have noticed. I think it is caused by the tiny amount of carbs in the fat bombs and soup stock, as well as the body utilising the last of the glucose stores in the muscles. This increase in sugar never lasts long. You can see here that it increased from 6am to 6:20am. The sugar level was taken from a stable 7mmo/l up to 10mmol/l.
  5. Then it becomes a waiting game. I take zero carbs, and wait for my sugar levels to drop. I know they will. It usually takes over an hour. I check my Continuos Glucose Monitor all the time. Blood sugar stays stable at around 9-10mmol/l for 90 minutes.
  6. Then, over the course of the next 60 minutes, my sugar level slowly descends from around 9mmol/l to 5mmol/l.
  7. I don’t let it drop below 5mmol/l, and therefore I take my glucose supplements that I carry with me. I use Dextro Tabs, where each tab is approximately 3g of carb. I end up taking 10 tablets as I am feeling my sugar levels dropping further. So I take a total of 30g carb around the 2:30 hour mark.
  8. You can see over the next 20 mins that my blood sugar levels stabilise and then drop again. At this point, I am feeling very poor on the marathon. I am not thinking clearly, and just trying to survive.
  9. Instead of taking more Dextro Tabs, I elect to take some coke at the water stations. I take a small serving of coke (100ml) at each of the last 3 water stations. This is a total of 300ml of coke or a further 30g of carbs.
  10. You can see what this extra boost of carbs did for my sugar level in the last 30 mins of the race.
  11. Immediately after the race, my sugar levels stabilised at 9mmol/l.
  12. About half an hour after the race, my sugar level started to increase again. I think this is a result of taking coke too close to the end of the race, and not having enough exercise to burn it up. I should have stopped drinking coke about 30 mins before the end.
  13. I corrected this high blood sugar by taking insulin, and then I treated myself to a binge meal (and beer – I did just complete a marathon after all 🙂 ) and that caused the last spike in sugar around 12:30pm.

So there you have it. 4 hours massive effort on 60g carb, and the 60g ended up being probably about 10g too much.

Comparatively speaking, 1 Gu gel is 22g of carb.

LCHF is the answer!

 *Dietitian and colleague Caryn Zinn aptly changed the acronym. It works.

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