Table 1.

PICOS (Population, Intervention, Comparison, Outcomes and Study design) criteria for inclusion and exclusion of studies in the systematic review

Population	General population, 10–40 years, living in Europe, the USA, Canada, Australia or New Zealand
	Results specifically presented in adolescent (i.e. 10–17-year-old) and/or young adult (i.e. 18–40-year-old) subgroups
	Excluded: patients, elderly, infants or pre-school children, pregnant or lactating women, overweight or obese persons, those participating in a diet programme, persons with eating disorders, specific ethnic groups (e.g. Inuit), low-income countries or geographic areas such as Asia
Intervention	Not applicable
Comparison	Of participants, their parents, their household:
	Socio-economic status: education level, income, occupation, employment status
	Family structure: matrimonial status, parenthood, sibling(s), household size
	Cultural aspects and migration status: country of origin, language spoken, migration background
	Excluded: socio-economic status of a geographic area, a school or another non-individual level
Outcome	Diet assessed by usual intake or food frequency, in terms of food groups, food patterns and diet scores
	Excluded outcomes: energy, macro- and micronutrient intakes, eating behaviour (meal frequency, breakfast skipping, takeaway or fast-food consumption) and diet assessed through biomarkers
Study design	Cross-sectional
	Longitudinal: description of cohort at baseline or at follow-up point