Understanding individual differences in sweet taste liking and their implications for obesity: an interdisciplinary approach

Liking for sweetness and consumption of high fat-sugar diets are hot topics in ingestive behaviour, where controlling excess sugar intake is the focus of dietary guidelines and public health policies to tackle obesity and associated non-communicable diseases globally. As taste hedonics strongly influence food choices and intake, they may heighten susceptibility to overconsume obesogenic diets, leading to weight gain. However, contrary to the persuasive view that sweet liking is universal, half a decade of empirical evidence demonstrates distinct hedonic responses to sweetness with a three-phenotype model prevailing in Europe, North America, and Asia: extreme sweet-likers, moderate sweet-likers and sweet-dislikers. Nevertheless, the underlying drivers and their relationship to broader eating habits, behaviours and anthropometric measures remain largely unknown and complicated by inconsistent liking classification methods, relatively small samples, and an overreliance on BMI. Therefore, to address these gaps, this thesis used an interdisciplinary approach to investigate what is currently known about the sweet-liking phenotypes (Chapter Two) and how they relate to wider anthropometric measures (Chapter Three), liking and intake of foods implicated in obesogenic diets (Chapter Four) and their underlying drivers by assessing for the first time their heritability using twin modelling and the shared genetic and environmental influences with related traits (Chapter Five).

Overall, this thesis challenges the notion of universal sweetness liking and highlights the importance of disentangling the conventional belief that a strong liking for sweetness drives overconsumption. There was no clear evidence that greater sweet liking was associated with worst anthropometric profiles in an individual participant data meta-analysis, nor overconsumption of obesogenic foods in a follow-up study. However, these differences appear to be partially heritable and may be explained through enhanced reward sensitivity and homeostatic mechanisms, where enhanced introspective abilities may act as protective mechanisms to prevent overconsumption in those with the greatest liking for sweet tastes.