The Energy Factor the Code Assigns to Dietary Fibre
Schedule 11 of the Food Standards Code sets out the energy factors used to calculate the energy content on a nutrition information panel. Dietary fibre is categorised as "unavailable carbohydrate" and assigned a factor of 8 kJ per gram, compared with 17 kJ/g for carbohydrate that isn't fibre, 37 kJ/g for fat, 17 kJ/g for protein and 29 kJ/g for alcohol. These factors are multiplied by the average quantity of each component to calculate the total energy value declared on the panel.
Why Fibre Carries Less Energy Than Other Carbohydrates
Regular carbohydrate is digested and absorbed in the small intestine, yielding its full energy value directly. Dietary fibre, by definition, resists that process. Some of it passes through entirely unabsorbed. The rest is fermented by bacteria in the large intestine into short-chain fatty acids, some of which are absorbed and used for energy, but this is a less efficient, indirect route than straightforward digestion. The 8 kJ/g figure reflects that only part of fibre's potential energy ends up available to the body, and how much varies by fibre type and how fermentable it is.
How It Shows on the Nutrition Panel
The panel's single "Energy" figure already has fibre's lower factor baked in: it's calculated from protein, carbohydrate, fat, alcohol (where present) and dietary fibre together, each at its own energy factor, then added up. Fibre isn't ignored in the energy total, it's just weighted lower than the other carbohydrate on the panel.
Australian vs US Labels: Carbohydrate and "Net Carbs"
Australian panels keep dietary fibre as its own line, separate from the "Carbohydrate" figure, consistent with the Code's lower energy factor for fibre. US labels declare "Total Carbohydrate," which includes fibre within it rather than listing it separately at a different energy value. "Net carbs" (typically total carbohydrate minus fibre, and sometimes minus certain sugar alcohols) is a term used in some diet and marketing contexts, not a defined term in either the Australian or US regulatory frameworks.
Sources
- Australia New Zealand Food Standards Code, Schedule 11, Calculation of Values for Nutrition Information Panel
- Australia New Zealand Food Standards Code, Standard 1.2.8, Nutrition Information Requirements
- Energy and Nutritional Aspects of Dietary Fiber in Human, Journal of Health Care and Research