Investigating the eating behaviours of free-living low-carbohydrate diets users in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics, Massey University, Albany, New Zealand

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Background: Many individuals adopt a low-carbohydrate (low-CHO) diet as a weight management approach. Eating behaviours are a crucial determinant of dietary intake and health, however, their relation to low-CHO diet users has scarcely been assessed. Aim: This study aimed to investigate the body compositions, dietary intakes, and eating behaviours of free-living, self-reported low-CHO diet users in NZ and how they differed between CHO intake groups. Methods: This cross-sectional study recruited men and women aged 20-45 years following a low-CHO diet for at least four months. Participants completed a health and demographics questionnaire, the Three-Factor Eating Questionnaire (TFEQ), a 4-day weighed dietary record, and provided anthropometric measurements. Participants were grouped into three CHO intake ranges defined as moderately low (ML) (>100 and <150 g/day) (n=10), low (L) (≥50 and <100 g/day) (n=20), and very-low (VL) (<50 g/day of CHO) (n=39). Results: Sixty-nine individuals with a mean age of 35 years participated in this study. Their mean macronutrient intakes as a contribution to total energy were 12.5 ± 8.28% for CHO, 58 ± 11.3% for total fat, 22.6 ± 6.98% for saturated fatty acids (SFA), and 24.5 (23.3-25.9) % for protein. Total fat and SFA (%EI) increased as CHO intake decreased, while protein intake was similar in each CHO group. They had a mean body fat percentage (BF%) of 27.9 ± 9.9% and a median muscle mass of 28.0 [25.2-33.2] kg. Body composition was similar in each CHO group. Overall, participants showed high restraint, low rigid and flexible restraint, low disinhibition, low habitual, situational, and emotional disinhibition, low hunger, and low internal and external hunger. TFEQ scores did not differ significantly between CHO groups. Restraint was positively associated with CHO (%EI) (r = 0.34, p = <0.01) and inversely associated with total fat (r = -0.35, p = <0.01) and SFA (%EI) (r = -0.31, p = 0.01). CHO intake (%EI) was positively correlated with rigid restraint (r = 0.27, p = <0.01) and flexible restraint (r = 0.34, p = <0.01). Restraint correlated with BF% (r = 0.28, p = 0.02), and each increasing restraint score predicted a 0.6% increase in BF%. As diet duration increased, BMI (r = -0.27, p = 0.03), WC (r = -0.28, p = 0.03), and habitual disinhibition (r = - 0.27, p = 0.03) decreased. Conclusions: Our findings suggest that low-CHO diet users exhibit high dietary restraint, low disinhibition, and low hunger. Restraint may increase as CHO intake increases and fat intake decreases. BF% was accompanied by high restraint. It is important to consider the associations eating behaviours can have with dietary intake and body composition in low-CHO diets in determining the suitability of such a diet.