Carb Loading – A Diabetic’s Dilemma


Eating is as important as training for a runner’s ability to perform. This is something I had to learn the hard way.

When I trained for my second marathon, I found I was going low during my long runs. In fact, I finished my longest pre-marathon run with a blood sugar level of 37 (at that point I – idiotically – wasn’t  testing during runs).

In an attempt  to avoid lows during the marathon itself,  I decided to limit the amount of insulin I took.  I did so by not eating carbohydrates the day before the race and also the morning before the race. The not so stellar logic here was that if I didn’t take much insulin, I wouldn’t have any lows the night before the race or during the race itself. I also thought that limiting my carbohydrate intake would keep me from going high. At the time, this all made perfect sense.  As sensible as it may have seemed, the result proved otherwise.  I suffered from a huge lack of energy during the race and a had very big collision with “the wall” at the 21-22 mile.

For my third marathon, in Rotterdam, I tried a different method.  I decided to eat some carbs the night before (pizza – again, not one of my best ideas), but I wasn’t scientific about it.  And because I was on the road with other non-diabetic runners, I had a hard time separating myself from the group and  taking care of my own, very complicated nutritional needs (I know, I know… lack of self discipline and planning).

It’s taken me a while but I have finally understood that I must find a way to fill my carbohydrate stores without losing control of my blood sugar. I’ve spent a fair amount of time reading about “carb loading” and I am starting to understand a little bit about it.

I found a great article by Benjamin Rapoport, who aside from holding a personal marathon record of 2:50 (according to Runner’s World) is also studying medicine at Harvard Medical School and engineering at MIT Department of Electronic Engineering and Computer Science (M.D – Ph.D program). Rapoport’s article explains the importance of carbohydrates during endurance activities and results of not having sufficient reserves. He explains how to calculate the amount of carb a runner needs for a marathon. He also created an online calculator to help runners calculate the amount of carbohydrates they need to consume before the race.

For most runners, eating is the bonus they have while training. They get to enjoy lots of pasta, rice and bread.  For me, it is an everlasting dilemma.  I know my performance depends on consuming carbs, but I also know that every time I start eating large amounts of them I have blood sugar control issues – highs and lows. So I’ve chosen my carbs to fit in with the Caveman Diet (following the guidelines of the Paleo Diet for athletes – adjusted for diabetes) and I have tried to carefully consume them before my runs. Eating more before long runs and less before shorter ones, but always trying to keep my muscles fueled.

I’m eight weeks away from my next marathon and I just completed my first 20 mile run in 2 hours and 55 minutes. I made sure to eat a lot of carbs the day before –sweet potatoes and quinoa – and reduced my long acting insulin to 10 units instead of my usual 14 units. I paced myself correctly and found my pace increased throughout the run making for a negative split. I used energy gels, one after the first 15 minutes the second 45 minutes later and then one every half hour. My blood sugar was 165 starting out and remained at that level throughout the run (I checked ever 6-7 miles). I hope I do this well on my next marathon.

I’m starting to really rack up the miles now. I have 4-5 weeks of hard running ahead of me before I start to taper. The key is to stay healthy and injury free. That means sleeping and eating correctly.

Total miles for this week: 41

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Maureen Seel
Maureen Seel
3 years ago

You’re so much faster than me LOL. I’m finally looking into carb loading after having a hard time with bonking around 14-16 miles. The prospect of eating so many carbs and taking so much insulin is intimidating. I’m on a pump and continuous glucose monitor which allows some creativity and flexibility…I guess we’ll see. I have 18 miles planned Sunday.

12 years ago

I don’t know if it helps at all, but I would like to give you some info from my experience with running. Last year, I was training for a half-marathon in July, I run all outdoors, and I had gotten up to 11 miles when I stress injured my femur a month before the race and had to stop for about 3 months. Anyways, I am also type 1 diabetic, on the insulin pump, and I experimented a lot with my bs and running. I used to always start my runs with some food, I was worried about crashing. BUT… Read more »

Scott K. Johnson
Scott K. Johnson
12 years ago

Nice!  There’s so much trial and error, and the body is such a magical machine, isn’t it?

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