Glycemic index vs glycemic load, with the arithmetic
GI ranks a food against glucose at a fixed 50 g of carbohydrate. Glycemic load scales that to the amount you actually eat. One line of arithmetic separates them.
Nothing here can diagnose you, and nothing here is a treatment plan. Blood glucose results are interpreted by a doctor alongside your history, your symptoms and a repeat test — a single number on a screen is not a diagnosis. If any reading concerns you, or if you feel unwell, see a doctor rather than a website.
Glycemic index is a ranking, not a property you can look up in a composition table. To produce one, volunteers eat a portion of the food containing 50 g of available carbohydrate, their blood glucose is sampled repeatedly over two hours, and the area under that curve is compared with the same person's response to 50 g of pure glucose. Glucose scores 100 by definition.
That design has an obvious weakness. Fifty grams of available carbohydrate is a small bowl of rice and an enormous quantity of carrot. Ranking them against each other at that fixed carbohydrate load says very little about eating either of them.
Glycemic load fixes the portion problem
glycemic load = glycemic index × available carbohydrate in the portion (g) ÷ 100
Take a jowar roti. Its measured GI is 84.1, which is high. A 60 g roti carries about 29.6 g of available carbohydrate on the figures from the same study, so the glycemic load of one roti is 84.1 × 29.6 ÷ 100 ≈ 24.9. High GI, and a high glycemic load too — in this case both point the same way.
Now take white chickpea sundal, measured at GI 24.1. A 100 g bowl carries 22.3 g of available carbohydrate, giving a glycemic load of about 5.4. Low on both.
The two measures diverge whenever a food's carbohydrate is dilute. A food can have a high glycemic index and a small glycemic load simply because a normal portion contains very little carbohydrate — which is exactly the case that makes GI-only advice misleading.
The standard categories
Low GI is 55 or less, medium 56 to 69, high 70 or more. For glycemic load, per serving: low is 10 or less, medium 11 to 19, high 20 or more. The tables on this site show both.
Four reasons to hold these numbers loosely
- GI is measured on individual foods, and you eat meals. Fat, protein, acid and fibre eaten alongside a carbohydrate all change the response, and a roti eaten with dal and sabzi is not the roti that was tested.
- Cooking moves it. Boiling time, parboiling, cooling and reheating all change the glucose response of the same starch. Rice is the clearest example — published GI values for rice span most of the scale.
- Person-to-person variation is large. Published GI values carry a standard deviation, and several of the Indian values on this site have one of five points or more.
- Low GI does not mean low calorie. Adding ghee to a dish lowers its glycemic index and raises its energy content. A number moving in a direction you like is not the same as a decision being a good one.
Glycemic index is useful as one input among several. It is not a scoring system for food, and it is certainly not a treatment. If you have diabetes or prediabetes, what to eat is a conversation with a doctor or a registered dietitian who knows your results — not something a table settles.
PeakForm is a training and accountability programme. It is not a treatment for diabetes or prediabetes, it is not a substitute for your doctor's advice, and nothing on this site should be acted on before speaking to one.
Common questions
How do you calculate glycemic load?
What counts as a low glycemic index?
Is glycemic index reliable?
More guides
General information only — NOT medical advice, and never a diagnosis. Only a doctor can interpret your results and diagnose or treat diabetes. If a reading concerns you, see a doctor rather than a website. Every threshold, equation and glycemic index value used on this site is listed with its publication on the data & method page.