Tired of the Glycemic Index (GI) focusing solely on carbs?
Discover the Glucose Score – a game-changer for managing blood sugar.
In this article, we unveil how to use both tools effectively.
- Learn why stable blood glucose matters and how the GI works.
- Explore who developed it and how it’s calculated.
- But the real gem is the Glucose Score, which measures the blood sugar response to food.
Dive into the impact of carbs, protein, fat, and fibre on your glucose levels. Find out why lower-carb options are key for stability and why protein shines.
We’ll show you how to compare GI, Glycemic Load, and Glucose Score, making meal planning a breeze. Plus, we have charts galore for easy reference.
Ready to master your blood sugar? Join us on this journey into the world of the Glycemic Index and the Glucose Score.
- Why Stable Blood Glucose Is Important
- What is the Glycemic Index?
- What Is the Glycemic Load?
- Who Developed the Glycemic Index?
- How Is the Glycemic Index Calculated?
- What Is a Good Glycemic Index Score?
- What is the Glucose Score?
- Glucose Score Data
- How Do Carbs, Protein, Fat, and Fibre Impact Your Glucose?
- Net Carbohydrate vs Glycemic Index vs Glucose Score
- Protein vs. Glucose Score vs. Satiety Index
- Low Glycemic Index Meals and Recipes
- Low Glucose Score Meals
- Glucose Response to Carbohydrates vs. Fat
- Limitations of the Glycemic Index & Glucose Score
Why Stable Blood Glucose Is Important
In a world awash with diabetes and insulin resistance, optimising your blood glucose is a big deal! Elevated glucose is generally a sign of poor metabolic health and insulin resistance, often stemming from obesity.
The more your glucose rises, the more likely it is to come crashing back down. This leads to increased hunger, eating sooner, and overeating less-optimal foods at the next meal (i.e., reactive hypoglycemia).
While chronically elevated blood glucose leads to many complications over the long term, it’s the crash in glucose that you should be aware of to avoid excessive hunger and maintain consistent energy levels.
Additionally, people like my wife and son who have Type-1 Diabetes, along with the growing number of people with insulin-dependent Type-2 Diabetes, often struggle to match large doses of insulin with large intakes of fast-acting carbohydrates.
Per Dr. Bernstein’s Law of Small Numbers, meals that cause a smaller rise in glucose require less insulin and smaller errors that are easier to correct. So, understanding which foods raise glucose the most vs. the least can be helpful to optimise blood glucose control.
What is the Glycemic Index?
The glycemic index (GI) usually measures how much 50 g of carbohydrates in a food raises blood glucose levels relative to white bread (which has a score of 100).
- Foods with a high GI value are rapidly digested and absorbed. This causes a rapid spike in blood sugar.
- Foods with a lower GI value are absorbed more slowly and raise blood sugar levels more gradually.
What Is the Glycemic Load?
Although a food may have a high GI, it won’t raise your glucose much if you only eat a little bit of it. Portion size matters. While you might be able to eat a few bowls of cereal, it’s hard to eat a lot of spinach. Thus, it will have a lower Glycemic Load.
Glycemic Load (GL) considers the quantity of carbohydrates in a food and how quickly the body metabolises them. The formula for calculating Glycemic Load is:
- Glycemic Load = GI x net carbs
Thus, Glycemic Load is a more accurate indicator of a food’s effect on blood sugar levels than the Glycemic Index alone because it accounts for the quantity and quality of carbohydrates in a food.
Who Developed the Glycemic Index?
The Glycemic Index was developed by Dr David J. Jenkins and colleagues at the University of Toronto in the early 1980s. The GI has since become one of the most widely used tools for people with diabetes trying to manage their blood sugar levels.
How Is the Glycemic Index Calculated?
The GI is calculated by feeding ten metabolically healthy subjects a portion of food containing 50 grams of carbohydrates and measuring their blood glucose over the next two hours.
The area under the two-hour blood glucose response for the food is then calculated. The same ten subjects are later fed a high-glucose food (e.g., white bread), and the area under the curve glucose response is calculated. The ratio between the two responses is the Glycemic Index.
Unfortunately, one of the limitations of the GI data is that it is usually only tested on high-carb foods and thus excludes higher fat and higher protein foods.
What Is a Good Glycemic Index Score?
Generally, foods with a GI that’s less than 55 are considered ‘low’-Glycemic Index foods. Conversely, foods with a glycemic index greater than 70 are considered ‘high’, and those in the middle are considered ‘moderate’.
- Low-Glycemic Index foods – less than 55
- Medium-Glycemic Index foods – 55 to 69
- High-Glycemic Index foods – greater than 100
If you are someone with T2D or severe metabolic syndrome, it’s recommended to prioritise low-GI foods.
What is the Glucose Score?
The Glucose Score allows us to compare the glucose response to any food, not just high-carbohydrate foods!
Glucose Score Data
In our previous article, Making Sense of the Food Insulin Index, we used data from the University of Sydney to estimate the insulin response to a wide range of foods based on their macronutrient properties. Our analysis showed that carbohydrates elicit the most significant insulin response, but protein and fat impact insulin to a lesser degree.
The same group that developed the original Food Insulin Index and Satiety Index were also involved in the ongoing expansion and testing of the Glycemic Index, with GI testing undertaken alongside the Food Insulin Index testing as well as testing the Glucose Score.
Dr. Kirstine Bell’s 2014 thesis, Clinical Application of the Food Insulin Index to Diabetes Mellitus, included the expansion of the Food Insulin Index and Glucose score to include 147 foods. The testing also included the Glycemic Index for these foods as well.
How Do Carbs, Protein, Fat, and Fibre Impact Your Glucose?
To understand how each macronutrient influences GI and GS, I ran a multivariate regression analysis on the data to understand the most statistically significant parameters impacting the average rise in glucose after eating.
For the Glycemic Index data, I found:
- Non-fibre carbohydrates raise glucose the most, while
- Fibre reduces the impact of carbohydrates (by 19%), and
- Fat has 20% of the impact of non-fibre carbohydrates.
For the Glucose Score data, I found:
- Non-fibre carbohydrates raise glucose the most, while
- Fat has a small positive impact (7% of non-fibre carbohydrates); and
- Fibre has a negative effect on GI (-6% of non-fibre carbohydrates).
While protein does raise insulin, it doesn’t raise glucose. Instead, protein has a slight negative impact on glucose. However, it was not statistically significant in the analysis, so it was not included.
For more on the impact of protein on glucose and insulin, see:
- Does Protein Spike Insulin (and Does It Matter)? and
- Why Does My Blood Sugar Drop (or Rise) After Eating Protein?
Net Carbohydrate vs Glycemic Index vs Glucose Score
The regression coefficients from the multivariate analysis allow us to calculate the Glucose Score of any food.
To illustrate, the chart below shows net carbs vs Glucose Scores for six-hundred popular foods with our Optimisers.
The colouring is based on our Satiety Index Score. Foods in green (like bok choy, cabbage and tuna) are hard to overeat, whereas foods shown in red (like cream, oil, and chocolate brownies) are much easier to overconsume.
To dive into the details, you can view the interactive Tabluea version here on your computer. If you mouse over each point, you’ll see more details on each food, like the macros, nutrient density, satiety score and food insulin index.
So what does all this mean?
As you might expect, high-carb foods like watermelon, rice, and raisins shown towards the right have a higher Glucose Score and will raise glucose quickly.
The middle of the chart shows that high-satiety, high-fibre, non-starchy veggies have a high glycemic index. However, consuming a substantial portion of these foods is challenging, so they may not cause a significant rise. Nutritious, higher-satiety foods will have a lower glycemic load because we won’t be able to eat as much of them.
Meanwhile, we see both high-protein, high-satiety foods shown in green towards the far left and high-fat, low-satiety foods in red towards the left. Both of these types of foods have minimal GI scores.
Overall, this data demonstrates that lower-carb foods will help to stabilise your blood glucose. However, although either fat or protein will keep your glucose stable, it’d be best to prioritise protein over fat for greater satiety, particularly if weight loss is a goal.
Protein vs. Glucose Score vs. Satiety Index
Things get more interesting when we look at protein % vs. Glucose Score in the following chart.
We see towards the right that higher-protein foods tend to have a lower GS. Generally speaking, lower-protein foods towards the left tend to provide less satiety. In comparison, higher-protein foods towards the right provide greater satiety and help keep your glucose stable.
Again, you can dive into the details of this chart in the interactive Tableau version here and mouse over the foods to see more info.
Low Glycemic Index Meals and Recipes
While looking at individual foods is interesting, we combine them into meals.
The following chart shows the 1000+ recipes we have prepared for our suite of NutriBooster recipe books in terms of Glycemic Index vs. Diet Quality Score. Again, the colouring is based on our Satiety Index Score.
Notice the cluster of high-satiety meals (green) towards the top left; here, we see a ton of nutrient-dense, lower-glycemic recipes. Diet quality and satiety tend to align, too. The most nutritious and high-satiety recipes tend to have a substantial protein % and lower GI scores.
You can dive into the details of these charts using the Tableau link here. If you click on a recipe, you will see a popup box with more information that includes a link at the bottom to view an image of the recipe.
Many Optimisers in our Macros Masterclass get lost for hours in this chart, finding all the recipes they want to try.
Low Glucose Score Meals
For completeness, the chart below shows the glucose score vs diet quality score, showing a similar trend to the Glycemic Index chart above.
You can dive into all the data in the interactive Tableau chart here and view photos of each recipe.
If you’re interested, you can learn more about our suite of NutriBooster recipe books here. If you’re already part of our Optimising Nutrition community, you can download samples of each NutriBooster recipe book here.
Glucose Response to Carbohydrates vs. Fat
Overall, this data analysis shows that a lower-carb diet aligns with more stable blood glucose, which, to many, is self-evident. But before we wrap up, it’s worth mentioning a few caveats around the risks of merely optimising your diet for stable blood glucose.
The chart below was taken from an NIH study. It shows the glucose response to high-fat (red line) vs. high-carb (green line) meals. Notice how glucose peaks 45 to 60 minutes after a high-carb meal, whereas there is a lower response to high-fat meals.
In addition to stabilising blood glucose, a lower-carb diet tends to improve greater satiety. This is in part from its greater protein % content and in part because it does not raise and crash blood sugar to the extent of high-carb meals.
As the chart below from our satiety analysis shows, moving from the typical carb-and-fat combo blend to a diet with 10-20% carbs aligns with a 25% reduction in energy intake.
If your only goal is stabilising your blood glucose, swapping carbs for fat is OK. However, if your goal is also to stabilise blood glucose, lose weight, and improve your metabolic health, it’s ideal to prioritise protein and other nutrients to increase satiety rather than doubling down on dietary fat.
As shown in the final chart below, prioritising foods with a higher protein % (i.e. less energy from fat and carbs) aligns with eating fewer calories.
Limitations of the Glycemic Index & Glucose Score
Finally, it’s important to highlight one of the most significant pitfalls of the Glycemic Index and the Glucose Score data: they only measure the rise in glucose two hours after eating.
While a significant spike in glucose is not ideal, it’s more important to watch out for foods that raise your blood glucose and keep it elevated for a long time. Hyper-palatable, ultra-processed foods contain an ‘addictive’ blend of carbohydrates and fat, with minimal fibre, protein, minerals and vitamins.
These are the low-satiety foods that we find are the easiest to overeat. While they may not ‘spike’ your blood glucose as much, they will elevate your glucose and insulin the longest, leading to fat gain.
In our Macros Masterclass, we guide our Optimisers to reduce their carbohydrates if their glucose rises above the healthy range. Then, once they’ve got their carbohydrates dialled in, we advise them to find foods and recipes they enjoy eating that allow them to dial back dietary fat to lose body fat and improve their metabolic health.
- The Glycemic Index measures how much a food raises blood glucose two hours after eating. However, the Glycemic Index data tends to be limited to higher-carbohydrate foods.
- Using multivariate regression analysis, we found that carbohydrate has the most significant impact on glucose, fat plays a minor role, and fibre reduces the effects of carbohydrates.
- The coefficients from the regression analysis allow us to estimate the Glycemic Index and Glucose Score of any food or meal.
- Foods and meals with a lower Glycemic Index and Glucose Score that contain more protein also tend to provide more nutrients per calorie (i.e., nutrient density) and, thus, greater satiety. Therefore, these nutritious foods and meals would be more optimal for weight loss than higher-fat options.