%0 Journal Article %T Objectively Measured Physical Activity and Body Mass Index in Preschool Children %A Susana Maria Coelho Guimar£¿es Vale %A Rute Marina Roberto Santos %A Lu¨ªsa Maria da Cruz Soares-Miranda %A Carla Marisa Maia Moreira %A Jonatan R. Ruiz %A Jorge Augusto Silva Mota %J International Journal of Pediatrics %D 2010 %I Hindawi Publishing Corporation %R 10.1155/2010/479439 %X Aim. To examine the association between objectively measured physical activity (PA) and body mass index (BMI) in preschool children. Methods. The study comprised 281 children (55.9% boys) aged from 4 to 6 years. PA was measured by accelerometer. Children were categorized as non-overweight (NOW) and overweight/obese (OW) according to the sex-adjusted BMI z-score ( 1 and 1, resp.). Results. Total and moderate intensity PA were not associated with BMI. We observed that a higher proportion of OW children were classified as low-vigorous PA compared to their NOW peers (43.9 versus 32.1%, resp., ). Logistic regression analysis showed that children with low-vigorous PA had higher odds ratio (OR) to be classified as OW compared to those with high-vigorous PA ( ; 95% CI: 1.4¨C13.4; ) after adjusting for BMI at first and second years of life and other potential confounders. Conclusion. The data suggests that vigorous PA may play a key role in the obesity development already at pre-school age. 1. Introduction The prevalence of childhood obesity has been rising during the past decades in many parts of the world [1]. In Portugal, there is a high prevalence of overweight and obese children [2] and adolescents [3]. This picture is particularly alarming owing to the increasing risk of developing cardiovascular diseases in overweight and obese individuals [4, 5]. Over the long term, childhood/adolescence overweight is strongly associated with adult obesity [6, 7]. Therefore, it is of clinical and public health importance to examine the risk trends in order to develop effective preventive strategies targeting those at risk start as early as possible. Human obesity is a multifactorial disorder where both genes [8] and lifestyle factors, including diet and physical activity [9] are important contributors. Both maternal and paternal body mass index (BMI) has also a strong influence on offspring¡¯s risk of obesity [10, 11]. Other determinants of childhood obesity include birth weight and weight gain that occur during the first years of life [12¨C14]. It has been suggested that obesity during the pre-school years is associated with other clinical factors easily assessed at birth [15]. For instance, it was found an association between birth weight and the risk of being obese in children at the age of 4, 8, 10, and 12 years [16]. Besides the previously mentioned factors, there exist other potentially modifiable factors that increase the risk of overweight in childhood and adolescence. These include: (i) intrauterine life: excessive gestational weight gain [17, 18], and maternal %U http://www.hindawi.com/journals/ijpedi/2010/479439/