The four NOVA groups and where they divide
The NOVA system classifies foods by the extent and purpose of processing rather than by nutrients. Group 1 is unprocessed or minimally processed foods (fresh fruit, plain grains, eggs). Group 2 is processed culinary ingredients (oils, butter, sugar, salt) used to prepare other foods. Group 3 is processed foods made by adding group 2 ingredients to group 1 foods (canned vegetables, cheese, fresh bread). Group 4 is ultra-processed foods built largely from industrial formulations and additives.
The classification is about how a food is made, not a simple verdict on nutrients, which is why two foods with similar labels can fall in different groups.
What associations with group 4 do and do not prove
Observational studies have linked higher intake of group 4 ultra-processed foods with several poor health outcomes, and this is an active research area. These are associations from population data, however, and do not by themselves establish that processing is the cause, since ultra-processed foods also tend to be energy-dense, salty, and easy to overeat.
This is general educational information, not medical or dietary advice. The framework is a useful lens, not a precise risk calculator for any individual; specific dietary concerns should be discussed with a qualified professional.