Classification of Foods by the Degree of Processing

The 4,644 reported foods, including preparations (e.g., natural milk with sugar, cooked rice, and lentil stew, among others), were categorized into one of four groups and then into subgroups according to the NOVA classification system (35, 36) as follows:

- Group 1, Unprocessed or minimally processed food: natural foods altered by processes such as drying, freezing, pasteurization, among others that do not add substances such as salt, sugar, oil, or fats to the original food; comprising 13 subgroups (e.g., milk and plain yogurt; fruits; legumes; meat).

- Group 2, Processed culinary ingredients: substances obtained directly from group 1 foods or from nature by processes such as pressing, refining, and milling, among others; comprising five subgroups (e.g., plant oils, table sugar, table salt).

- Group 3, Processed foods: relatively simple products made by adding sugars, oil, salt, or other group 2 substances to group 1 foods, with the main purpose of increasing the durability of group 1 foods or to modify their sensory qualities; comprising five subgroups (e.g., breads [fresh, unpackaged]; cheese; vegetables, fruits, and other plant foods preserved in brine or syrup).

- Group 4, Ultra-processed foods: industrial formulations typically with five or more ingredients, including the formulations used in group 3 and additives as anti-oxidants, stabilizers, preservatives, as well as substances not commonly used in culinary preparations whose purpose is to imitate the sensory qualities of group 1 foods or of culinary preparations of these foods or to disguise the undesirable sensory qualities of the final products; comprising 21 subgroups (e.g., milk-based drinks; sandwiches and hamburgers on a bun [ready-to-eat/heat]; cakes, cookies, and pies).

Detailed descriptions of each subgroup are provided as Supplementary Material.