Hunger and glycaemic response to meals with a high glycaemic index consumed in the morning or evening among students with earlier and later chronotype- ChroNu Study
Background:
Hunger and glucose homeostasis follow a circadian rhythmicity and might differ by their circadian phenotype, e.g. chronotype, particularly when consuming a meal with a high glycaemic index (GI). As young adults are vulnerable for dietary misalignment, this study investigates whether i) morning versus evening 2-hour post-prandial (2-h pp) glycaemic response to a high GI meal differs among earlier and later chronotypes, and whether ii) the chronotype is associated with circadian differences in hunger*.</I>
Methods:
Among 320 students aged 18-25 years those with the earliest (n=22) and latest (n=23) chronotype were invited to a randomized controlled cross-over nutrition trial. On the intervention days, participants received a high GI meal (GI=72) either in the morning (7 a.m.) or the evening (8 p.m.). All other meals had a medium GI (46-59). Glucose responses were recorded by a continuous glucose monitoring device. Hunger was estimated on a labelled magnitude scale. Paired T-Test was used to compare 2-h pp incremental area under the curve (iAUC), and differences in hunger before meal intake (morning vs. evening). The association between hunger and chronotype was analysed using multivariable linear regression.
Results:
Earlier chronotypes (mid-point of sleep 3:43 a.m.) showed higher 2-h pp iAUC responses in the evening than in the morning: iAUC 236 (±90) vs. 198 (± 87) mmol/L, p=0.04, while in later chronotypes (5:37 a.m.) responses were comparable: iAUC 213 (±112) vs. 208 (±96) mmol/L, p=0.96. Hunger was higher in the evening than in the morning (p<0.0001) but this difference was not associated with the chronotype (p=0.7).
Conclusion:
While glucose homeostasis deteriorated in earlier chronotypes over the day, later chronotypes showed similar glucose responses to a high GI meal consumed early in the morning and late in the evening. This suggests that glucose homeostasis among later chronotypes may be adversely affected also early in the morning following a high GI meal against the inner clock. The circadian rhythm of hunger seems to be independent of the chronotype.
Keywords:
chronotype, glucose homeostasis, glycaemic index circadian misalignment, hunger
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