What is the Difference Between the Glycemic Index, the Insulin Index and Insulin Load?

The glycemic index (GI) compares the rise in blood sugar for a particular food relative to glucose.  The theory goes that it is better to eat low glycemic index carbohydrates that will not raise our blood sugar too much and will take longer to digest.

BONUS: FREE Video Lecture “Making sense of the food insulin index”

Building on the glycemic index is the concept of glycemic load which is the GI of a food multiplied by the grams of carbohydrate eaten.  Watermelon has a very high GI value, however, because watermelon only contains a small quantity of carbohydrates (watermelon is mostly water) the overall glycemic load is small.  A large glycemic load occurs when you eat a large quantity of a high glycemic index carbohydrate.

The limitation of the GI approach is that we can eat a diet full of low glycemic index carbohydrates and protein while still producing a large amount of insulin.  Even though they are slow to digest and do not raise blood sugar significantly, a low GI moderate GL diet will still require substantial amounts of insulin.  It’s the amount of insulin, not the grams of carbohydrates or even the rise in blood sugar that’s really at the nub of the problem.

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The chart below shows the relationship between the glycemic load and insulin index.  Reducing the glycemic load does not guarantee a low insulin response, particularly when it comes to high protein foods.

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Even if you’re eating low GI foods that don’t spike your blood sugars you may still be generating a sustained requirement for insulin.  Maintaining reasonable blood sugars in spite of a moderate glycemic load is just an indication that your pancreas is still keeping up, for now.

Various studies have shown that eating a low GI diet doesn’t help with weight loss. [4] [5]  We also now know that high insulin levels are also a massive health risk as well as high blood sugars. [6]

Rather than focusing on the glycemic load or the glycemic index, I believe it is more important to manage the overall insulin load of the diet, particularly if your aim is to achieve optimal blood sugars or reduce excess body fat.

Read more about the Food Insulin index

  1. Making sense of the Food Insulin Index
  2. What foods raise your blood sugar and insulin levels (other than carbs)?
  3. The insulin load… the greatest thing since carb counting!
  4. Does protein raise blood sugar?
  5. The blood glucose, glucagon and insulin response to protein
  6. Insulin calculator for Type 1 Diabetes (including protein and fibre)
  7. What is the difference between glycemic index, the insulin index and insulin load?
  8. Nutrient-dense foods for stable blood sugars and nutritional ketosis


[1] http://www.glycemicindex.com/

[2] http://sydney.edu.au/science/people/jennie.brandmiller.php

[3] https://www.diabetesaustralia.com.au/Living-with-Diabetes/Eating-Well/Glycaemic-Index-GI/

[4] http://www.ncbi.nlm.nih.gov/pubmed/17823436

[5] http://chriskresser.com/is-the-glycemic-index-useful

[6] http://high-fat-nutrition.blogspot.com.au/2014/12/accord-and-musings-on-insulin.html

19 thoughts on “What is the Difference Between the Glycemic Index, the Insulin Index and Insulin Load?”

  1. I have learned much from Dr. Fung’s videos. I’m glad I found them through this blog.

    However, there has always been one thing that bothered me about these types of articles. “If you must eat, don’t eat carbs”. This is kind of like telling people not to put gas in their car. Carbs are the energy source for everything we do. Carbs and fat. You have to have some level of carbs in your system. Unless my understanding of biology is incorrect, if you were to go on a zero carb diet and stay on it permanently, you would eventually die.

    So it would be helpful if these people made clear that “don’t eat carbs” is not a program you can follow forever. Carbs are a natural part of the food chain. It is simply that we eat them to excess, as we do so many other things, that is the problem. Unless I am completely mistaken.

    I know, trust and respect a biologist who worked on the human genome project. I’m going to drop him a line and ask him that question specifically. I’ll follow up when I hear back from him.

    • I suggest you read “The World Turned Upside Down” to get the full context.

      In the first chapter he says he said this as a joke at a conference, but then goes on to elaborate on the virtues of fasting, low carb and carbs that don’t raise your blood sugar.

      In the end you need glucose, but as Rosedale will tell you, you can get that glucose via gluconeogenesis from protein.

      I think you need to consider the total glucose load of your diet, not just carbs. That is, what proportion of the diet could convert to glucose in the system and require insulin.

      I’m intrigued by the idea that there must be a ‘goldilocks’ zone of carbs plus protein that will provide adequate energy without excess insulin that would lead to fat loss.

    • The glycemic stuff is baloney. It was created using NON-DIABETICS and while I agree with the dangers of extra insulin, excess insulin is a response to excess glucose which comes from excess carbs and to a lesser degree excess protein. Treat the disease not the symptoms. control your carb and protein intake and you’ll have less glucose and less insulin response to deal with.

      Diabetic t2 a1c 5.2
      Meds free for 2 yrs

      • Not if you have reactive hypoglycemia (non-diabetic) like me. My insulin overreacts and is
        different to “normal” and diabetics. Still trying to work out how to manage it. Clearly eating massive amounts of carbs aka DAA or diabetes australia recommends is just asking for constant hypos all day long, but even low carb I still deal with blood sugars below 4 for most of the day. Its quite frustrating trying to find the correct way to eat to avoid hypos and even harder to work out how to correct a hypo and not trigger another hypo 90 mins later. I hope with time, research and trial and error I work it out.

    • “You have to have some level of carbs in your system” – but you don’t have to eat them. The US IoM and others agree “The minimum level of dietary carbohydrates compatible with life is apparently zero”. Can you name a disease of carbohydrate deficiency ?

      So yes, you are mistaken.

      As a French scientist discovered, a dog eats no sugar but you can find sugar in the body of a dog – your liver will maintain blood glucose levels.

  2. So I said I’d ask my biologist friend and post what he had to say. This was his answer:

    To answer your Q, Yes, years ago, before all the nuances and alternate pathways of human metabolism were so fully understood it was believed that carbohydrates in some form (fats, sugars, starches…)were necessary to fuel the Citric Acid Cycle (CAC) in mitochondria to generate energy for the whole body (in the form of ATP) and glucose for use by the brain. The carbs could come either from your diet or your own body. But it is now known that in the absence of carbs the body can catabolize amino acids from proteins in your food and use the products as fuel. Specifically, under these low carb conditions the liver produces what are known as ketone bodies which cannot be metabolized by the liver itself but instead travel in the blood to the brain where they are used as an efficient fuel to power the CAC. There can be problems with overproduction of these ketone bodies if your diabetes is not well controlled, but if you’ve got a handle on that then there is no real physiological NEED for carbs. And apparently studies have shown that, at least for a matter of months, your body does not begin to cannibalize its own muscle mass -people actually lose a lot of their fat weight and PUT ON muscle. Sounds good to me.

    However, even if you’re really trying, I think it would be really difficult to exclude ALL carbs from your diet. I mean, you gotta have some bacon, right?

  3. Just got a revision, so I’m posting it here for clarity.

    Yikes. On re-reading what I shot off to you yesterday I realize in my haste I threw fats in with carbs. This is of course an absurd mistake. Fats are broken down into fatty acids, eventually to acetyl CoA, which can be used for energy in the CAC -by all cells except neurons.

      • The issue I have been having so far is that if I skip a meal or two my blood sugar immediately plummets to unsafe levels and I start experiencing the symptoms of hypoglycemia. So I am not sure how best to reduce my carbs without passing out at work or something.

      • Are you a type 1 or type 2? Sounds like you’re on insulin.

        You’ll probably have to wind back your medications as you ease into the LCHF or IF approach while carefully monitoring your blood sugars.

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