Understanding the complexity of diet in type 2 diabetes prevention : appetitive traits, dietary patterns, energy and nutrient intake

Eating behaviours and dietary intake are modifiable determinants of type 2 diabetes (T2D) risk, yet gaps remain in understanding their roles in influencing metabolic outcomes. This dissertation aimed to assess (i) associations between appetitive traits and metabolic outcomes and (ii) dietary changes and their associations with metabolic outcomes across two studies conducted within Small Steps for Big Changes (SSBC), a 4-week, community-based diabetes prevention program (DPP) targeting diet and exercise. In Study 1, a cross-sectional analysis was conducted (n=115 adults with prediabetes; age: 61.8±10.9years; 64.3%female) to assess appetitive traits using the Adult Eating Behaviour Questionnaire. Among females, Food Responsiveness was positively correlated with body mass index and waist circumference (WC). Among males, Emotional Overeating was positively correlated with hemoglobin A1c (HbA1c), whereas Slowness in Eating was negatively correlated with HbA1c. In Study 2, a retrospective analysis of a separate SSBC cohort (n=326; age:58.7±8.1 years; 77.0%female) assessed dietary intake via a brief food frequency questionnaire. Intakes of fruits, red meat, and bread changed significantly by 12 months following SSBC. Vegetable and fruit intake were negatively associated with body weight, while sweets, and bread intake were positively associated. Fruit intake was also negatively associated with WC, whereas bread intake was positively associated. Diet-by-time interactions were observed for vegetable and red meat intake in relation to body weight over 12 months. In Study 3, a prospective longitudinal analysis was conducted in the same cohort as Study 1, employing an image-based dietary assessment method. Energy, carbohydrate, and fibre intake, as well as body weight and WC, decreased significantly by 6 months following SSBC. Changes in carbohydrate and fibre intake were negatively associated with body weight. Collectively, this dissertation highlights that appetitive traits are associated with metabolic outcomes relevant to T2D risk, and that even modest dietary changes in vegetable, fibre, and red meat intake achieved through participation in a community-based DPP contribute to improvements in these outcomes. Inverse or attenuated associations between dietary intake and metabolic outcomes may reflect limitations in dietary assessment or non-dietary influences, underscoring the need for future research to examine the contribution of the exercise component of SSBC to metabolic improvements.