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The science behind the score

Built on evidence, held to honesty.

Every meal you photograph gets one number out of one hundred, a tier, and a few sentences explaining why. This page explains where that number comes from — and, just as honestly, what it doesn't claim.

Three foundations.

Block 01
Processing comes first.

The starting point of every score is how processed the foods on the plate are. For this, Nørra follows the NOVA classification — the framework developed by researchers at the University of São Paulo and used by the Food and Agriculture Organization of the United Nations, which groups foods from whole and minimally processed through to ultra-processed. A plate built from whole ingredients starts from a stronger base than one built from ultra-processed products. This is the single largest influence on any Nørra score, and it is a deliberate choice: a growing body of research — including a randomized controlled trial at the US National Institutes of Health and a 2024 umbrella review in The BMJ — has focused scientific attention on the degree of food processing, not just nutrient numbers.

Block 02
Balance follows the principles behind Europe's food labels.

The way Nørra credits protein, fiber and vegetables, while counting salt, sugars and saturated fat against a meal, follows the same nutrient-profiling principles that underpin Nutri-Score — the front-of-pack label officially adopted in France, Germany, Belgium, Spain, the Netherlands, Switzerland and Luxembourg. Nørra is independent: we are not affiliated with or endorsed by Nutri-Score or any government body. We follow the published principles because they are the most thoroughly studied nutrient-profiling approach in Europe.

Block 03
Thresholds follow the World Health Organization.

Where the score draws lines, it draws them in the directions WHO guidance points: limiting salt (WHO recommends less than 5 grams per day), free sugars (less than 10% of daily energy), and saturated fat (less than 10% of daily energy). Alcohol counts against a meal's score, consistent with the WHO's 2023 statement that no level of alcohol consumption has been established as safe. Sugary drinks are treated separately and strictly, in line with WHO's guidance on free sugars.

How a single meal is read.

Step 1
Identify.

Nørra reads the plate: what's there, roughly how much, and how it was likely prepared.

Step 2
Set the base.

The processing level of the ingredients sets the starting score, following NOVA.

Step 3
Credit what's genuinely there.

The meal earns credit for quality protein, fiber and whole grains, a variety of plants, nuts, and nutrient-dense ingredients.

Step 4
Count what works against it.

The meal loses ground for high salt, added sugars, saturated fat, refined carbohydrates, deep-fried preparation, and heavily processed components.

Step 5
Explain.

You get the score, its tier, and a few sentences on why. The explanation is held to the same standard as the score itself: it only says what the analysis actually supports. If an ingredient worked against the meal, Nørra won't praise it — even in an otherwise excellent plate.

What raises a score, and what lowers it.

Raises

  • Whole and minimally processed ingredients
  • Quality protein
  • Fiber and whole grains
  • A variety of plants on the plate
  • Nuts
  • Nutrient-dense ingredients

Lowers

  • High salt
  • Added and free sugars
  • Saturated fat
  • Refined carbohydrates
  • Deep-fried preparation
  • Heavily processed components
  • Sugary drinks
  • Alcohol

What we don't claim.

The directions of the score — what earns credit and what counts against a meal — are anchored in the sources on this page. The exact weights — how far each factor moves the number — are our own design decisions, made so that the score stays readable, consistent, and honest across very different meals. No published paper prescribes those weights, and we won't pretend one does.

A photograph is an estimate. Portion sizes read from a single image carry real uncertainty, which is why Nørra shows approximate values and lets you adjust portions — rather than pretending to gram-level precision it doesn't have.

The score describes the composition of a meal. It is not medical or dietary advice, and it makes no promises about health outcomes. If you have specific dietary needs or a medical condition, a qualified professional beats any app — including ours.

References.

  1. Monteiro CA, Cannon G, Levy RB, et al. Ultra-processed foods: what they are and how to identify them. Public Health Nutrition. 2019;22(5):936–941.
  2. Monteiro CA, Cannon G, Lawrence M, Costa Louzada ML, Pereira Machado P. Ultra-processed foods, diet quality, and health using the NOVA classification system. Rome: Food and Agriculture Organization of the United Nations; 2019.
  3. Hall KD, Ayuketah A, Brychta R, et al. Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake. Cell Metabolism. 2019;30(1):67–77.
  4. Lane MM, Gamage E, Du S, et al. Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses. BMJ. 2024;384:e077310.
  5. Deschasaux M, Huybrechts I, Julia C, et al. Association between nutritional profiles of foods underlying Nutri-Score front-of-pack labels and mortality: EPIC cohort study in 10 European countries. BMJ. 2020;370:m3173.
  6. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet. 2019;393(10170):434–445.
  7. Aune D, Keum N, Giovannucci E, et al. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies. BMC Medicine. 2016;14:207.
  8. World Health Organization. Guideline: Sugars intake for adults and children. Geneva: WHO; 2015.
  9. World Health Organization. Guideline: Sodium intake for adults and children. Geneva: WHO; 2012.
  10. World Health Organization. Saturated fatty acid and trans-fatty acid intake for adults and children: WHO guideline. Geneva: WHO; 2023.
  11. Anderson BO, Berdzuli N, Ilbawi A, et al. Health and cancer risks associated with low levels of alcohol consumption. The Lancet Public Health. 2023;8(1):e6–e7. (Statement of the World Health Organization.)
  12. World Health Organization. Healthy diet. Fact sheet. Geneva: WHO.

Questions about how the score works? Write to us — hello@norraapp.com.