Effect of plain versus sugar‐sweetened breakfast on energy balance and metabolic health: A secondary data analysis stratified by participant-defined sweet preference
Authors: Carroll Harriet 
Published: August 2020

Background: Variability in sweet preference between people is well established, with those who have a high preference colloquially identified as having a sweet tooth. Although characteristics have been described demonstrating key differences between those with and without a sweet tooth (such as differences in body mass index), it is less clear whether sweet preference moderates appetite and health responses to stimuli of different sweetness levels.Objective: To explore appetite and health responses to a sugar-sweetened (SWEET) and unsweetened (PLAIN) porridge-based breakfast, according to whether participants identified as having a sweet tooth or not. Methods: Secondary data analysis of a previously published randomised crossover trial in which n = 29 participants consumed an isocaloric PLAIN (~8 g sugar) and SWEET (~32 g sugar) porridge-based breakfast for three weeks each. Fasted pre- and post-intervention measures included blood biomarkers of health and appetite hormones, anthropometrics and metabolic rate, and a series of questionnaires assessing psychological appetite/approach to food. During each three week intervention, four days of lifestyle monitoring were conducted on days 1-4 and days 15-18, involving weighed food diaries, physical activity measurements (ActiHeart™), and visual analogue scales of appetite across the day. After study completion, participants were asked whether they believed they had a sweet tooth or not; n = 27 responded and were included in these analyses. Analyses were exploratory with no significance testing or a priori hypothesis. Results: 16 participants reported not having a sweet tooth. Average body mass index was higher in those without a sweet tooth (25.9 ± 6.0 kg/m2 versus 24.4 ± 4.3 kg/m2 for those with a sweet tooth), but waist-to-hip ratio was lower. Having a sweet tooth was associated with a higher desire for sweet across the day during both interventions compared to those without a sweet tooth, but also lower sugar intake. Sweet sensory-specific satiety was achieved in both groups post-breakfast during SWEET, whilst savoury sensory-specific satiety was achieved post-breakfast after both PLAIN and SWEET. Fasting plasma fibroblast growth factor 21 was higher in those with a sweet tooth, whilst fasting glucagon-like peptide-1 increased pre- to post-PLAIN (Δ 6.2, 95 % CI 1.1, 11.4 pmol∙L-1), but was otherwise similar across interventions and between groups. Those without a sweet tooth reduced their energy intake from week 1 to week 3 of PLAIN (Δ -152, 95 % CI -349, 45 kcal/d), whereas those with a sweet tooth (less reliably) increased their energy intake (Δ 131, 95 % CI -131, 395 kcal/d). No changes in energy intake were noted during SWEET. Physical activity energy expenditure largely remained consistent between groups and across interventions, though those without a sweet tooth increased their physical activity energy expenditure from week 1 to week 3 of SWEET (Δ 166, 95 % CI -8, 241 kcal/d).Conclusion: Having a sweet tooth was associated with distinct characteristics, such as lower body mass index and higher fasted plasma fibroblast growth factor 21 concentrations. Sweet preference may moderate biopsychological metabolic and appetitive responses to savoury or sweet primes. Due to the small sample size and other methodological features of these analyses, future work should establish the causality of these findings, and may need to consider sweet preference a priori when designing health and appetite research relating to sweetness.