📚 GI basics
What is the Glycemic Index (GI)?
The Glycemic Index (GI) is a ranking of carbohydrate-containing foods based on how quickly they raise
blood glucose after you eat them. In lab testing, GI compares a food’s blood sugar response to a reference (usually
pure glucose). A higher GI generally means a faster rise in blood sugar; a lower GI means a slower rise.
Here’s the important nuance: GI is measured under controlled conditions, usually on a single food with a fixed amount
of available carbohydrates. Real life isn’t controlled. You eat meals — not isolated glucose. That’s why this tool is
called an estimator. It helps you reason about the most important factors that change glycemic response:
fiber, protein, fat, processing, and cooking method.
GI vs Glycemic Load (GL)
People mix these up. GI is about the speed of blood sugar rise. Glycemic Load (GL) includes portion size.
A food can have a high GI but a low GL if you eat a small portion. Conversely, a low-GI food can become a big glycemic
hit if you eat a giant serving.
In simple terms:
- GI: “How fast does this carb act?”
- GL: “How big is the carb hit for this portion?”
If you’re managing diabetes, use CGM readings and clinician guidance. This tool is for education and meal planning.
🧮 How this estimator works
Macro + processing model (simple and useful)
Because we can’t run a human glucose trial in a browser, this estimator uses a practical approach:
it starts with a “carb-forward” base GI assumption and applies adjustments based on variables that consistently lower
glycemic response in real meals.
Step 1: Compute net carbs
We start with net carbs = total carbs − fiber (never below zero). Fiber slows digestion and reduces the
speed of glucose entry into the bloodstream.
Step 2: Apply slowing factors
Protein and fat slow gastric emptying and reduce the rate at which carbs show up as glucose. We apply a gentle downward
adjustment based on grams of protein and fat per serving.
Step 3: Apply processing and cooking effects
Processing and cooking can increase GI by making starch more accessible:
- Highly refined foods (white bread, sugary cereals) tend to act faster.
- Soft/overcooked starches tend to act faster than firm/al dente versions.
- Blended/mashed foods often act faster because physical structure is broken down.
The output is an estimated GI score and a category:
Low (≤55), Medium (56–69), High (≥70).
Use this as a planning tool, not a lab result.