Growth, body composition, physical activity and motor performance of Peruvian children, youth and siblings. Probing the effects of the environment.

Abstract

In this thesis different facets of human variability in physical growth, body composition, physical activity and motor performance are described and interpreted as end-results of adaptive processes in Peru different socio-geographical, educational and cultural contexts - especially children, youth and siblings living at sea-level, Amazon region and high-altitude. The data comes from the three research projects, developed in synchrony, between 2009 and 2010: "The Peruvian Health and Optimist Growth Study", "The Peruvian Sibling Study on Growth and Health" and "The Peruvian Family Study on Growth and Health". From the first project, a sample of 10795 children and adolescents (aged 6-17 years) was used. From the second project, 1618 biological siblings (aged 6 to 15 years) from 758 nuclear families were considered. From the third project, 247 biological siblings (aged 6 to 17 years) from 234 nuclear families were investigated. All data is hierarchically distributed within two nested domains: individual and environmental. Statistical analyses were done in R, SPSS, SuperMix and STATA softwares. Results showed that: (i) Peruvian children and adolescents' physical growth spurt parameters vary according to sex and geographic area, revealing a widespread variation when compared to other populations; (ii) the early growth "retardation" (stunting) negatively influenced children's physical fitness, being specific for each sex, age and physical fitness component; (iii) the variability in body composition, physical fitness and motor coordination is explained by individual characteristics, as well as natural (geographic area of residence) and built (school context) environments; (iv) the direction and magnitude of the results varied in function of the phenotype and predictors used; (v) changes in sibling resemblance depend on sib-type and the phenotype considered; (vi) individual characteristics and shared natural environment were differently associated with Peruvian siblings' health-related physical fitness components and physical activity phenotypes. This thesis highlighted a set of issues that emphasize the importance of considering the specificities of cultural and social strata of each geographical region, as well as the complex and entwined relationships of the individual, familial and environmental characteristics when designing intervention strategies to promote children and adolescents' healthy growth and sustainable development.