Tools & References

Glycemic Index

The glycemic index (GI) is simply a speed rating: how fast a food turns into blood sugar. Fast is the problem. Here is how to read it, and why it matters more than the label ever tells you.

The idea in one line

GI is the speedometer for food

Every carbohydrate eventually becomes blood sugar. The glycemic index measures how quickly that happens, on a scale from 0 to 100, compared to pure glucose. A high-GI food arrives like a flash flood. A low-GI food arrives like a steady stream.

Your body handles the steady stream beautifully. The flash flood forces a big insulin surge, and that surge is what leads to the afternoon crash, the cravings, and, repeated for years, insulin resistance. Slower is calmer, and calmer is what lasts.

The scale

Low, medium, high

BandGI scoreWhat it means
Low55 or underSlow, gentle rise. The terrain you want most days.
Medium56 to 69Fine in context, especially with protein and fat alongside.
High70 and upFast flood. Best kept occasional, and never on an empty stomach.
Real examples

Same food group, very different speeds

LOW GI (55 or under)
  • Most non-starchy vegetables
  • Berries, apples, pears
  • Lentils, chickpeas, beans
  • Plain Greek yogurt
  • Steel-cut oats
  • Nuts and seeds
MEDIUM GI (56 to 69)
  • Sweet potato
  • Basmati rice
  • Whole-grain bread
  • Banana (ripe)
  • Corn
  • Honey (small amounts)
HIGH GI (70 and up)
  • White bread and bagels
  • White rice, most cereals
  • Baked potato
  • Rice cakes, pretzels
  • Cornflakes and puffed cereals

Two honest limits before you use this

GI is not fixed. The same food shifts with ripeness, variety, how it is cooked and how long it is cooled. A firm banana and a speckled one are not the same number, and reheated cooled potato is lower than freshly baked. Treat these bands as a map, not a measurement.

GI alone will mislead you, and juice is the clearest example. Unsweetened orange juice sits around 50 and apple juice around 41, both technically low GI, while cola is around 63, only medium. Yet nobody would call a glass of juice a calm choice for blood sugar. The reason is that GI ignores how much carbohydrate is actually in the serving. That is exactly the gap Glycemic Load was invented to close, and it is why sugary drinks belong in that conversation rather than this one.

The same caution applies in reverse: chocolate lands near 40 to 45 because its fat slows absorption, and french fries near 63. Low on this scale does not automatically mean good for you.

"The fastest way to calm your blood sugar is to slow your food down."
Three ways to lower the GI of any meal
Add protein and fatThey slow digestion, so the same carbohydrate arrives gently instead of all at once.
Eat the carbohydrate lastVegetables and protein first, starch last, flattens the spike from the identical plate.
Keep it wholeWhole fruit beats juice, steel-cut beats instant. Fibre and structure slow everything down.
Walk it offA ten-minute walk after eating pulls glucose into muscle without an extra insulin surge.

One honest caveat: GI is measured for a food eaten alone, on an empty stomach. Real meals mix foods, which changes the number. That is why glycemic load, the next page, is the more practical tool.

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SourcesAtkinson FS, Foster-Powell K, Brand-Miller JC. International tables of glycemic index and glycemic load values. Diabetes Care, 2008. • Jenkins DJA, et al. Glycemic index of foods. American Journal of Clinical Nutrition, 1981. • Shukla AP, et al. Food order affects postprandial glucose and insulin. Diabetes Care, 2015.
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