Effect of meal timing on postprandial glucose responses to a low glycemic index meal: A crossover trial in healthy volunteers.
Level 2 - randomized trial
Crossover intervention trial in healthy human volunteers
PubMed 29248250 · doi:10.1016/j.clnu.2017.11.010
What was done
Healthy volunteers completed two testing protocols. First, an oral glucose tolerance test (OGTT, n = 10) was conducted at 08:00 (morning) and 20:00 (evening) to establish baseline diurnal glucose response. Second, participants (n = 9) consumed an identical low glycemic index (GI) meal (3.3 MJ, 48% carbohydrate, 40% fat, 11% protein, 22 g fiber) across three separate sessions at 08:00, 20:00, and 00:00 (midnight). Blood glucose and insulin were measured over a 3-hour postprandial period, and incremental area under the curve (iAUC) was evaluated using Wilcoxon signed-rank tests.
What was found
In the OGTT (n = 10), evening glucose iAUC was higher than morning (p = 0.007). In the low GI meal trial (n = 9), glucose iAUC was higher at evening (p = 0.008) and midnight (p = 0.021) compared to morning, with no significant difference between evening and midnight (p = 0.594). Postprandial insulin iAUC was also significantly elevated at evening (p = 0.008) and midnight (p = 0.008) compared to morning. Absolute iAUC values and effect sizes were not reported in the abstract.
Why it matters
This study demonstrates that circadian-driven reductions in glucose tolerance and insulin sensitivity persist even when consuming low-GI, high-fiber meals, suggesting that nighttime meal timing alone impairs postprandial metabolic control.
Limits
The sample size was very small (n = 9 to 10), and the study examined only acute 3-hour postprandial responses in healthy volunteers rather than clinical populations or chronic shift workers. The abstract provides p-values but omits absolute glucose and insulin concentrations, standard deviations, and effect sizes.
Cited by
- supports Postprandial glucose response is significantly higher in the evening compared to the morning, and humans are more insulin sensitive in the morning.