Glycaemic Load: Why Portion Matters Alongside Glycaemic Index

GL = (GI × grams of available carbohydrate in the serving) ÷ 100. [2]

As a hypothetical example, a food with GI 60 and 30 g of available carbohydrate has a calculated GL of 18. With 15 g of carbohydrate from the same food, GL is 9. [2]

Conventional serving categories are low at 10 or below, medium at 11 to 19, and high at 20 or above. These describe servings, not personalised meal limits. [2]

GL is a portion-comparison tool, not a complete score for diet quality or metabolic health. A calculated score does not measure your glucose, insulin or body-fat change. [3] [4]

There is no established daily GL target for fat loss that suits everyone. A sustainable energy deficit matters more for weight loss than reaching an isolated GL score. [3] [4]

WHO judged GL associations with disease outcomes to be low-certainty and inconsistent. Observational findings do not establish that lowering GL causes a longer life. [3]

Fibre-rich carbohydrate foods have more consistent supporting evidence than pursuing the lowest possible GL. Consider food quality and variety alongside portions. [3]

GL can complement portion planning, but it does not replace carbohydrate counting when that is part of diabetes care. [4]

Training demands can guide carbohydrate amount, type and timing. The aim is to support the session and recovery, not simply to keep GL low every day. [5]

Start with portions you eat often: rice with a stir-fry, toast with jam, a 600 ml juice, a muesli bar and sweetened flat white, or mashed potato.

These examples cannot all be labelled high GL without serving and product details. Calculate from the amount actually eaten and an appropriate GI value. [1] [2]

Try lentils, chickpeas, black beans, oats, apples or berries as fibre-rich options. Choose foods for their overall nutritional value, not only their GL. [3]

For basmati rice, sourdough rye, pumpernickel or Vogel's-style bread, check the tested product and portion. A food name alone is not enough to assign its GL. [1] [2]

Halving a rice portion halves its contribution to calculated GL, assuming the same rice and preparation. It does not necessarily halve the whole meal's GL or your glucose response. [1] [2]

Try a smaller rice portion with more non-starchy vegetables and an appropriate protein serving. Protein and fat can change the glucose response, but adding them does not cancel carbohydrate. [4]

Where a report includes daily and meal-level GL estimates, use them to explore where carbohydrate portions are concentrated and how they fit around training.

Treat report scores and modelled curves as educational estimates, not measurements or diagnoses. GI testing measures an average glucose response under standard conditions, not your response to each meal. [1]

NZ FOODfiles 2024 provides nutrient composition data; GI values come from separate food testing. A GL estimate needs an appropriate GI match and the carbohydrate amount eaten. [1] [6]

FOODfiles describes typical NZ food composition, not exact values for every product or serving. Database matching makes estimates useful, not physiologically precise. [6]

Ask how missing food-log entries, recipes and foods without tested GI values are handled. An unexplained estimate should not be treated as an exact result.

In a study of 15 healthy adults, rice refrigerated for 24 hours at 4°C and reheated had more resistant starch and produced a lower glucose response than freshly cooked rice. [7]

This small, single-meal study does not establish a fixed GL reduction across rice varieties, potatoes or people. Do not automatically deduct a percentage from your food log. [7]

Refrigerate leftovers promptly, within two hours. Eat refrigerated rice within two days. If reheating, heat until piping hot throughout and reheat only once. [8]

If you use insulin or medicine that can cause low blood glucose, discuss substantial carbohydrate changes with your diabetes team. Do not change medication based on a GL estimate. [4]

You do not need to remove pantry staples wholesale. Start with one meal: check the portion, consider a fibre-rich swap, and keep the overall eating pattern varied. [3]