AimObesity tracks from childhood into adulthood. We evaluated the effect of early stimulation of physical activity on growth, body composition, motor activity and motor development in toddlers.MethodsWe performed a cluster randomised controlled single‐blinded trial in Dutch Well Baby Clinics, with seven nurses and 96 children (40% girls) randomised to the intervention group and six nurses and 65 children (57% girls) to the control group. Intervention nurses advised parents on stimulating motor development and physical activity during regular visits at 2 weeks and two, four, eight and 11 months. Baseline characteristics such as birthweight and mode of feeding were comparable. Outcomes at two‐and‐a‐half years included anthropometry, skinfold thicknesses, bioelectrical impedance analyses, motor development and daily physical activity. We used linear mixed models with nurses as cluster.ResultsWe evaluated 143 children (89 intervention, 54 control) as 18 dropped out. Skinfolds were significantly lower in intervention children (29.6 ± 4.7 mm) than controls (32.4 ± 6.0 mm), without differences in motor development or daily physical activity. Female interventions showed lower weight, skinfolds, waist and hip circumference.ConclusionAn activity stimulating programme during the child's first year improved indicators of adiposity when they were toddlers, especially in girls. Further research should determine whether these effects persist.