The QUebec Adipose and Lifestyle InvesTigation in Youth (QUALITY) Cohort study is a unique and comprehensive longitudinal study of 630 Caucasian children and their parents that was designed to investigate the natural history and determinants of childhood obesity and its cardiometabolic consequences.

The QUALITY Cohort is funded by the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Canada, as well as the Fonds de la recherche en santé du Québec. The multidisciplinary study team comprises over 20 researchers with a wide variety of relevant expertise as well as research fellows, students and staff (www.etudequalitystudy.ca).

The specific objectives of QUALITY are: 1) To increase understanding of the natural history of excess weight and its associated cardiometabolic consequences (dyslipidemia, hyperinsulinemia, dysglycemia, inflammation, elevated blood pressure, sympathetic overactivity) in youth at risk for the development of obesity; 2) To investigate the relative importance of the genetic, biological, environmental and psychosocial determinants of excess weight and its associated cardiometabolic consequences. Determinants of particular interest include social factors (socio-economic status, family composition, built environment), behavioural factors (eating behaviour, physical activity, smoking, sleep, stress), biological factors (adverse fetal environment, body fat distribution, growth trajectory, aerobic fitness), metabolic factors (insulin sensitivity, adipocytokines), and genetic/familial factors (family history, parental characteristics, gene variations); 3) To examine the relation between obesity, cardiometabolic complications, and subclinical markers of atherosclerosis; and 4) To examine whether obesity and its associated risk factor are related to children's oral health.

The QUALITY Cohort used a school-based sampling strategy to identify potential participants. About 400 000 recruitment flyers were distributed over three consecutive years to parents of children in Grades 2 to 5, in 1040 primary schools (89% of schools approached) including 44 private schools situated within 75 km of Montreal, Quebec City and Sherbrooke in the province of Quebec, Canada. Families interested in participating were invited to contact the research coordinator for additional information, to confirm eligibility, and to set an appointment with the research team; 1320 of 3350 families who contacted the coordinator met the inclusion criteria. Six hundred and thirty families agreed to participate and completed the baseline evaluation.

Inclusion Criteria:

• Children aged 8-10 years at baseline;
• Caucasian of Western European ancestry;
• At least one obese biological parent (i.e., body mass index (BMI) ≥30 kg/m2 or waist circumference >102 cm in men and >88 cm in women, based on self-reported measurements of height, weight and waist circumference)
• Both biological parents available to participate in the baseline assessment.

Exclusion Criteria:

• Children with a previous diagnosis of Type 1 or 2 diabetes;
• Children with a previous diagnosis of a serious illness, psychological condition, or cognitive disorder which hindered participation in some or all of the study components;
• Children treated with anti-hypertensive medication or steroids (except if administered topically or through inhalation);
• Children following a very restricted diet (< 600 kcal/day);
• Mother pregnant or breastfeeding at the baseline evaluation;
• Family with pending plans to move out of the province of Quebec (Canada).

630 Caucasian families with a child aged 8-10 years agreed to participate and completed the baseline evaluation.

564 families completed the second round of data collection 2 years later. 377 families completed the third round of data collection 7 years after the baseline assessment.

A 4th round of data collection is currently being prepared.