Longitudinal study of changes in body mass index, anthropometric measures, dietary intake and physical activity in cohorts of school-going Irish adolescents

The prevalence of obesity worldwide has increased dramatically over the last few decades. Poor dietary habits and low levels of exercise in adolescence are often maintained into adulthood where they can impact on the incidence of obesity and chronic diseases. A 3-year longitudinal study of anthropometric, dietary and exercise parameters was carried out annually (2005 - 2007) in 3 Irish secondary schools. Anthropometric measurements were taken in each year and analysed longitudinally. Overweight and obesity were at relatively low levels in these adolescents. Height, weight, BMI, waist and hip circumferences and TST increased significantly over the 3 years. Waist-to-hip ratio (WHR) decreased significantly over time. Boys were significantly taller than girls across the 3 years. A 3-day weighed food diary was used to assess food intake by the adolescents. Analysis of dietary intake data was determined using WISP©. Mean daily energy and nutrient intakes were reported. Mean daily energy and macronutrient intakes were analysed longitudinally. The adolescents’ diet was characterised by relatively high saturated fat intakes and insufficient fruit and vegetable consumption. The dietary pattern did not change significantly over the 3 years. Boys consumed more energy than girls over the study period. A validated questionnaire was used to assess physical activity and sedentary activity levels. Boys were substantially more active and had higher energy expenditure estimates than girls throughout the study. A significant longitudinal decrease in physical activity levels among the adolescents was observed. Both genders spent more than the recommended amount of time (hrs/day) pursing sedentary activities. The dietary pattern in these Irish adolescents is relatively poor. Of additional concern is the overall longitudinal decrease in physical activity levels. Promoting consumption of a balanced diet and increased exercise levels among adolescents will help to reduce future public health care costs due to weight-related diseases.

Nutrition, growth and body composition in preterm infants

The goal of neonatal nutrition in the preterm infant is to achieve postnatal growth and body composition approximating that of a normal fetus of the same postmenstrual age and to obtain a functional outcome comparable to infants born at term. However, in clinical practice such a pattern is seldom achieved, with growth failure and altered body composition being extensively reported. The BabyGrow preterm nutrition study was a longitudinal, prospective, observational study designed to investigate nutrition and growth in 59 preterm infants following the implementation of evidence-based nutrition guidelines in the neonatal unit at Cork University Maternity Hospital. Nutrient delivery was precisely measured during the entire hospital stay and intakes were compared with current international recommendations. Barriers to nutrient delivery were identified across the phases of nutritional support i.e. exclusive parenteral nutrition and transition (establishment of enteral feeds) phases of nutrition and nutritional strategies to optimise nutrient delivery were proposed according to these phases. Growth was measured from birth up to 2 months corrected age and body composition was assessed in terms of fat mass and lean body mass by air displacement plethysmography (PEA POD) at 34 weeks gestation, term corrected age and 2 months corrected age. Anthropometric and body composition data in the preterm cohort were compared with a term reference group from the Cork BASELINE Birth Cohort Study (n=1070) at similar time intervals. The clinical and nutritional determinants of growth and body composition during the neonatal period were reported for the first time. These data have international relevance, informing authoritative agencies developing evidence-based practice guidelines for neonatal nutritional support. In the future, the nutritional management of preterm infants may need to be individualised to consider gestational age, birth weight as well as preterm morbidity.

Nutrition, growth and body composition in infancy

This thesis is presented in two parts. Data for this research is from the Cork BASELINE (Babies after SCOPE, Evaluating Longitudinal Impact using Neurological and Nutritional Endpoints) Birth Cohort Study (n = 2137). In this prospective birth cohort study, pediatric follow-up with in-person appointments were repeated from the time of birth through to 2, 6 and 12 months, and at 2 years. Body composition was measured by air displacement plethysmography at birth and at 2 months using the PEA POD Infant Body Composition Tracking System. This thesis provides the first extensive report on the study’s 2 year assessment. In part one, the aims were to investigate potential early-life risk factors for childhood overweight and obesity, including rapid growth and body composition in infancy and umbilical cord concentrations of leptin and high molecular weight (HMW) adiponectin. This research is the first to describe rapid growth in early infancy in terms of changes in direct measures of body composition. These are also the first data to examine associations between umbilical cord leptin and HMW adiponectin concentrations and changes in fat and lean mass in early infancy. These data provide additional insight into characterising the growth trajectory in infancy and into the role of perinatal factors in determining infant growth and subsequent overweight/obesity risk. In part two of this thesis, the aims were to quantify vitamin D intake and status at 2 years and to investigate whether 25-hydroxyvitamin D [25(OH)D] concentrations in early pregnancy and in umbilical cord blood are associated with infant growth and body composition. There was a low prevalence of vitamin D deficiency among Irish 2 year olds (n = 742) despite a high prevalence of inadequate intakes and high latitude (51°N). Maternal 25(OH)D concentrations at 15 weeks gestation and cord 25(OH)D concentrations at delivery were not associated with infant growth or adiposity.