BackgroundNorth-south differences in the prevalence of obesity and fitness levels have been found in European adolescents, yet it is unknown if such differences already exist in very young children. ObjectivesThis study aims to compare the prevalence of overweight/obesity and fitness levels in preschool children aged 4 years from Sweden (north of Europe) and Spain (south of Europe). MethodsThe sample consisted of 315 Swedish and 128 Spanish preschoolers. Anthropometry (weight, height, waist circumference) and fitness (strength, speed-agility, balance and cardiorespiratory fitness) were assessed. Analysis of covariance adjusted for age, sex and height/body mass index (BMI) was used. ResultsPreschool children from Sweden had lower prevalence of overweight/obesity than their peers from Spain (World Obesity Federation, mean difference, MD=-9%, P=0.010; World Health Organization, MD=-11%, P=0.011). Concerning fitness, preschoolers from Spain were more fit in terms of upper-muscular strength (MD=+0.4kg, P=0.010), speed-agility (MD=-1.9s, P=0.001), balance (MD=+4.0s, P=0.001) and cardiorespiratory fitness (MD=boys=+6.6 laps, girls=+2.3 laps; P<0.001 for all), yet they had worse lower-muscular strength (MD=-7.1, P0.001) than those from Sweden. Differences in upper-muscular strength were largely explained by differences in BMI, and differences in cardiorespiratory fitness should be interpreted cautiously due to some methodological deviations. ConclusionsThese findings suggest that a higher prevalence of overweight/obesity in Spain compared with Sweden is present already at early childhood, while differences in physical fitness components showed mixed findings.