[Methodology of the 2023 ALADINO study: a national and international benchmark].

Obesity prevalence studies constitute a fundamental tool for the obesity surveillance and therefore for evidence-based decision-making, as well as for evaluating the effectiveness of policies aimed at improving diet, promoting health, and enhancing child well-being. The ALADINO 2023 study (Nutrition, Physical Activity, Child Development and Obesity) is an observational study conducted by the Spanish Agency for Food Safety and Nutrition (AESAN), with a descriptive cross-sectional design. Its objective was to determine the prevalence of overweight and obesity, their evolution over time, and the associated factors among schoolchildren aged six to nine years in Spain. The study is framed within the WHO European Childhood Obesity Surveillance Initiative (COSI) of the World Health Organization (WHO) European Region, following a standardised and harmonised protocol across the participating countries. The sample included 12,678 schoolchildren enrolled in 296 primary schools. Anthropometric data were obtained through direct measurements, while associated factors were assessed using questionnaires completed by families and educational centres. The strengths of this study include large sample size, measured anthropometric data, and an extensive battery of questions included in its questionnaires that allow for the collection of key information on weight status, especially obesity, lifestyles and sociodemographic aspects. The analyses conducted to obtain the results generated high-quality findings with national representativeness, which have also been incorporated into the COSI study, thereby constituting a national and international reference in the field of childhood obesity surveillance.