Influência da ordem de nascimento e do número de irmãos na composição corporal de adolescentes.

Abstract

The aims of the present study were to assess the influence of birth order and number of siblings on body composition in adolescents, and to evaluate the association between number of siblings and dietary patterns in adolescence. The study was conducted using data from the 1993 Pelotas Birth Cohort, in Brazil. At the age of 18 years, 4563 adolescents were located, of whom 4106 were interviewed (follow-up rate 81.3%). Of these, 3974 adolescents were included in our analysis with complete data on body composition and 3751 with data on dietary patterns. Body composition was assessed by fat mass index and fat-free mass index, both collected by air displacement plethysmography (BOD POD®). Principal component analysis was performed to identify dietary patterns. We identified four dietary patterns with a total variance of 40%, which we called ?Protein and fast foods?, ?Fruit and vegetables?, ?Sweets, soft drinks, and dairy products?, and ?Common Brazilian?. Crude and adjusted analyzes were performed using Linear Regression. A systematic review and metaanalysis were also performed. The objective was to examine the effects of birth order and number of siblings on overweight/obesity. Our findings showed that the number of siblings was the key influence on body composition, rather than the position that the adolescents occupy amongst siblings. Only children of both sexes were more likely to have higher fat mass index compared to those who have siblings. Girls who have no siblings presented the lowest levels of fat-free mass while boys without siblings had greater body mass index. Also, adolescents with a higher number of siblings had a higher adherence to ?Protein and fast foods?, ?Fruit and vegetables?, and ?Sweets, soft drinks, and dairy products? patterns. In conclusion, our results showed that the number of siblings influences both body composition and dietary patterns of adolescents. Higher number of siblings was associated to a more diverse diet among the adolescents, higher fat-free mass index, and lower body mass and fat mass indices. Thus, the research highlights the need for intervention programs focusing on adolescents who are only children.