What is the difference between glycemic index and glycemic load?
Patient's Query
Doctor, I am very confused about food advice in diabetes. Many doctors told me to avoid high glycemic index foods, so I started checking lists online. Then I stopped eating certain fruits like watermelon because I read it has a high glycemic index.
Later, one of my friends told me watermelon is actually allowed in diabetes and said something about glycemic load. That confused me even more. Some say watermelon is bad, some say it is fine.
Now I do not know what to follow. What exactly is glycemic index and what is glycemic load? Which one should I really look at in daily life? Can you explain this in a simple, practical way so I can apply it without getting scared of food?
Doctor Answers
This confusion is very common, and you are asking the right question.
Let me simplify it.
Glycemic index (GI) tells you how fast a food raises blood sugar compared to pure glucose. It is about speed.
Glycemic load (GL) tells you how much total sugar load that food gives based on the portion you eat. It is about quantity.
A simple rule to remember is this:
What you eat affects glycemic index. How much you eat affects glycemic load.
Let us look at this in a small table.
Term | What it means | What it depends on |
Glycemic Index | Speed of sugar rise | Type of food |
Glycemic Load | Total sugar impact | Type of food + portion size |
Now let us take your watermelon example.
Watermelon has a high glycemic index, around 70 to 75. That means the sugar from watermelon is absorbed quickly.
But watermelon is mostly water. A normal serving has very little total carbohydrate. So the glycemic load of one small slice is low.
That means:
- A small bowl of watermelon causes only a mild sugar rise
- Eating a whole large plate or half a watermelon will cause a big sugar rise
So watermelon is not “bad” by itself. The portion decides the problem.
The same logic applies to all foods.
- Guava is considered diabetes-friendly, but eating 8 to 10 guavas will raise sugar
- Rice has a high glycemic index, but a very small portion may still fit into a meal plan
This is why focusing only on glycemic index can be misleading. Glycemic load gives a more practical, real-life picture.
For daily life in diabetes:
- Prefer low to moderate glycemic index foods
- Control portion size to keep glycemic load low
- Eat fruits in moderation, not in large quantities
- Combine fruits with meals, not as large standalone snacks
Food fear is not the goal. Understanding quantity is the key.
References:
- https://www.health.harvard.edu/diseases-and-conditions/the-lowdown-on-glycemic-index-and-glycemic-load
- https://www.sciencedirect.com/science/article/pii/S0002916523239131
- https://www.who.int/publications/i/item/924120916X
- https://diabetesjournals.org/care/article-abstract/42/5/731/40480/Nutrition-Therapy-for-Adults-With-Diabetes-or
Disclaimer: The information provided in this Q&A is for educational purposes only and should not be considered as medical advice. Always consult with a qualified healthcare professional for personalized medical guidance and treatment recommendations.