Making Sense of the Glycaemic Index


Mid October, I went to the DiabetesSisters Weekend for Women conference Alexandria, Virginia. See disclaimer at the end. One of the outstanding presentations I attended was by Thriveabetes 2016 speaker, Gary Scheiner’s presentation on “Making use of the Glycaemic Index”. This should not be a surprise to anyone has read Gary’s book “Think Like a Pancreas”. I will be honest here; when I heard the words “Glycaemic Index” I pretended I didn’t. And the reason is that several years ago, when it became a thing that was relevant to diabetes management, I tried to learn but I found it completely and utterly confusing. So I went to Gary’s talk as a skeptic.

BUT! As always Gary puts the information together well. See his blog posts here.

He started by saying that the glycemic index is the speed glucose enters the blood in the first two hours. It does not measure how fast foods enter the blood as glucose beyond that or how long it takes at all. A-ha! Ok so glycemic index is useful information for first two hours. I feel exonerated now.

This is hugely relevant to my diabetes management because I know that my rapid acting insulin peaks in approx 2 hours and that I might need additional insulin doses after that to cover the glucose released into my blood after the two hours.

The glycemic index is measured from 0 to 100. The closer to 100 a Food is, the higher its glycemic index is and the quicker the glucose hits your blood.

Here is a snapshot of the other things I learned;

  • A mixed meal, ie a meal with protein, carbohydrates and or fat gravitates towards the carb. Meaning your body will process that first, albeit slower than if it was just carbs. So I might need to take a post meal dose of insulin in addition to my pre-meal dose.
  • If you have a low GI food before your meal it will slow down the follow up starch in your meal. This is really good to know! Bring on the peanuts before the pasta or pizza :-)
  • Larger portions take longer to digest. This isn’t new information to me but I suppose I always underestimate just how flippin’ long it takes.
  • Time since your last meal affects the glycemic index. If you are still processing your food from the last meal, it’s going to slow down glucose absorption even more.

Some additional pieces of information not related to glycemic index but valuable.

  • Don’t trust your CGM when you are recovering from a low. The lag time in full force.
  • Insulin on board pump feature doesn’t take into account the food on board. As mentioned in the previous paragraph, if you are still digesting food you may need to override the insulin on board recommendation.
  • Insulin resistance can happen if you have a meal with a lot of fat.
  • Protein to insulin formula = ½ The total of protein grams and treat as carbs.
  • Amylin/Symlin is a hormone that slows gastric emptying. People who don’t have insulin don’t have amylin either so stomachs process food quicker.
  • Victoza is a GLP-1 injectable medication and reduces glucagon secretion; slows down the absorption of food.

In summary, glycemic index important to people with diabetes because:

  • Satiety. Low glycemic index meals help you feel full for longer.
  • Helps with the Timing of insulin. For example, if you know a meal or snack is going to have a high glycemic index then you could take your insulin 15 - 20. Minutes beforehand to give it a head start.
  • Helps avoid post meal spikes

So, I’m glad that I learned all of this and I’m glad that I don’t have to waste any more of my time trying to figure it out because it makes more sense to me now. And It may help me to know the glycemic index of a Food I’ve never tried before so that I can figure how to deliver my insulin (pre-meal, at meal or extended Bolus).

Disclaimer: Diabetes Sisters paid for my conference registration and accommodation but also gave me a contribution towards my travel costs. All they asked for in return was that I would write a blog post about the conference which I had to do anyway because I learned so much that needs to be shared;-) And I wrote here about how I was selected.