Childhood Obesity in Ireland: Growth and Obesogenic Behavioural Patterns

Background and aims: Childhood obesity has been one of the most significant public health challenges of the 21st century and has both short-term and long-term consequences. The aim of this thesis was to investigate latent growth and behavioural patterns in childhood, their determinants and associations with cardio metabolic outcomes.

Methods: This thesis consists of three main studies. Initially, a systematic review, based on a pre-prepared protocol, was conducted to investigate group-based trajectory modelling of body mass index (BMI) in childhood, their determinants, and associations with cardio metabolic outcomes. Two observational studies were then conducted using data from the BASELINE birth cohort in Cork. The first study examined latent growth trajectories in the first five years using growth mixture modelling (GMM), and multivariable multinomial logistic regression was used to explore associated determinants. Following this, the second study investigated latent behavioural patterns in five year olds using latent class analysis, including eating behaviour, activity and sedentary behaviour, and sleep duration. Furthermore, multinomial logistic regression was used to explore potentially associated determinants and logistic regression used to examine potential associations between latent class membership and cardio metabolic outcomes.

Results: The systematic review resulted in 14 studies included, ranging in size from 246 to 12,050 children. Findings showed that high maternal pre-pregnancy BMI was the most frequently identified risk factor for membership of a rapid gain trajectory. Furthermore, significant associations between rapid weight gain and stable high trajectories and body measures at follow-up were identified in several studies. In the first study using BASELINE data, three trajectories were identified using GMM (normal, rapid BMI gain in the first six months, and rapid gain after 12 months). Male sex and higher maternal age increased the likelihood of 15 belonging to the rapid gain in the first 6 months trajectory. Raised maternal BMI at 15 weeks of pregnancy and lower cord blood insulin-like growth factor (IGF)-2 were associated with rapid gain after 1 year. In the second study, using LCA, three distinct groups/classes of children were identified based on eating behaviour, physical activity, TV use, and sleep at 5 years of age. Approximately half of children belonged to a normative class, while 28% of children were in a class characterised by high scores on the food avoidance scales (food fussiness, slowness in eating, and satiety responsiveness) in combination with low enjoyment of food, and 20% experienced high scores on the food approach scales (enjoyment of food, emotional overeating and food responsiveness). There was evidence that low socioeconomic index and no breastfeeding at 2 months were associated with the high food avoidance scale, low activity, and shorter sleep duration. Furthermore, there was evidence that children in this class were at a greater risk of overweight and obesity.

Discussion: Overall this thesis adds to the growing body of evidence investigating childhood overweight and obesity. The principal findings suggest interventions targeted at a high-risk growth trajectory in early childhood, with high prevalence levels of overweight and obesity at five years of age, as well as a behavioural pattern characterised by high risk eating behaviours, and low levels of activity could help reduce the risk of overweight and obesity. Furthermore, this thesis has identified novel findings on the association between growth trajectories in early childhood and IGF-2, as well as eating behaviour in the context of other lifestyle behaviours. However, further research is required before any definitive conclusions can be made regarding the relationship and potential implications for obesity prevention.