The weight status, diet quality, and nutritional and metabolic health status of Irish adolescents - past perspectives and current insights

Adolescence is a critical stage of growth and development and can be a period of enhanced vulnerability to health risks. Overweight and obesity (Ov/Ob) and consumption of poor-quality diets are among the leading contributors to the global burden of non-communicable diseases and are being identified as increasingly prevalent issues in younger age groups. There is a need for an assessment of the prevalence of these health risks and their potential associated causes and consequences amongst adolescents in Ireland. This thesis aimed to examine changes in the weight status and diet quality of adolescents in Ireland over time, to identify some of the factors that may be influencing the diet quality and risk of excessive adiposity in modern Irish adolescents, and to assess relationships between the body composition and quality of diets consumed with the nutrition status and metabolic health of this age group. Analyses are based on data from cross sectional, nationally representative food consumption surveys of Irish adolescents, encompassing time points ranging from 1990 to 2020. Anthropometric measurements and dietary intake data was compiled from these surveys to derive the prevalence of overweight/obesity (Ov/Ob) and quality of diets consumed by adolescents at different time points. Data related to socio-demographics, parental characteristics, lifestyle behaviours, and the biochemical nutritional and metabolic health status of Irish adolescents in 2020 was assessed for relationships with adolescent weight status and diet quality. There is a rising prevalence of adolescents living with Ov/Ob in Ireland, with 24% of adolescents affected in 2020 compared to 18% in 2006 and 13% in 1990. A socio-economic gradient of adolescent Ov/Ob has emerged in more recent years, with adolescents from the lowest affluence social class displaying a nearly 4-fold increase in odds of having a higher BMI in 2020 compared to those of high affluence backgrounds. There has been a modest improvement in the quality of diets consumed by adolescents between 2006 and 2020, with those in 2020 consuming less sugared drinks, fruit juices, and high-fat potato and grain products than those in 2006. However, >80% of adolescents in 2020 were still below the minimum RDA for vegetables, fruit, milk, and water. Having a parent, particularly a mother, affected by a higher weight status was the strongest driver of adolescent Ov/Ob and was also associated with a deterioration in diet quality. Adolescents with a higher weight status displayed substantially higher sedentary and screen time and had a higher daily consumption of low-nutrient, energy-dense foods. There was a high level of awareness amongst Irish adolescents of their weight status, and those living with Ov/Ob displayed an increased odds of engaging in a weight loss diet and of under-reporting their dietary intake. The most pertinent biochemical nutritional issues identified amongst adolescents in 2020 were Vitamin D deficiency, folate deficiency, and excessive salt intake for the total population, with an increased prevalence of Vitamin D deficiency observed amongst those with Ov/Ob. A higher diet quality was positively associated with biochemical measures of Vitamin D and folate. There was indication of a trend towards a more unfavourable metabolic profile amongst those with excessive adiposity, with BMI, % body fat, and waist circumference displaying significant positive associations with non-HDL blood lipids, HOMA-IR, and high sensitivity C reactive protein. This thesis highlights a growing prevalence of adolescent Ov/Ob and obesity related issues amongst Irish adolescents in more recent years and identifies a complex network of causal and consequential factors that are implicated in the health and nutrition status of this age group. These findings support future research, initiatives, and strategies to promote and protect adolescent health in Ireland.