Background Prevalence of glycolipid metabolism disorders is rising annually. Dietary patterns are recognized as key modulators of their pathogenesis. Improper eating habits cause circadian disruption, which can be mediated by multiple genes. Clarifying the role of different dietary methods is crucial to preventing the occurrence of metabolic diseases. However, relevant epidemiological data and data of population studies are scant.
Objective To investigate the effects of dietary frequency on human glycolipid metabolism and circadian gene expressions, thereby providing insights into the relationship between dietary frequency and disease risk in healthy populations.
Methods Healthy volunteers aged 18-29 years with regular sleep-wake cycles, regular dietary, and moderate snack intake were recruited between April and May 2022. Twenty eligible participants were randomized into two groups: a three-meal group (n=10) and a six-meal group (n=10) for a crossover intervention. Participants in the three-meal group consumed main meals at 7: 00, 12: 00, and 18: 00. Those in the six-meal group received three additional glucose challenges (75 g anhydrous glucose dissolved in 300 mL of water) at 10: 00, 15: 00, and 20: 00. Each intervention lasted 24 hours. Blood samples were collected at eight timepoints (7: 00, 8: 00, 10: 00, 12: 00, 13: 00, 16: 00, 20: 00, 2: 00) to analyze serum metabolic markers, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), glucose, insulin, and leptin. The mRNA expression levels of circadian genes were detected (Clock, Bmal 1, Per 2, Cry 1, Ppar α, Sirt 1) .
Results A significant interaction effect between group and time was observed on TG levels (Finteraction =2.277, Pinteraction =0.032). A significant main effect of group presented on LDL-C levels (Fgroup=4.803, Pgroup=0.030), while time exhibited a significant main effect on TC levels (Ftime=2.092, Ptime=0.048). No significant differences in TC, TG, LDL-C, or HDL-C levels were observed between the two groups at any time points (P>0.05). A significant interaction effect between group and time was identified for blood glucose levels (Finteraction =3.926, Pinteraction =0.001). The group showed a significant main effect on insulin levels (Fgroup=12.240, Pgroup<0.001), and time demonstrated significant main effects on blood glucose, insulin, and leptin levels (Ftime=10.840, 2.399, and 4.347, respectively; Ptime<0.05). Participants in the six-meal group exhibited higher blood glucose levels at 12: 00 and 20: 00, elevated insulin levels at 10: 00 and 16: 00, and lower leptin levels at 16: 00 compared to the three-meal group (P<0.05). A significant interaction effect between group and time was observed for the mRNA expression of Cry 1 (Finteraction =30.250, Pinteraction<0.001). Significant main effects of group were detected for the mRNA expressions of Clock, Bmal 1, Per 2, Cry 1, Ppar α, and Sirt 1 (Pgroup<0.05), while significant main effects of time were noted for the mRNA expressions of Bmal 1, Per 2, Cry 1, and Sirt 1 (Ptime<0.05). Participants in the six-meal group displayed significantly higher mRNA expressions of Clock at 8: 00 and 13: 00, Per 2 at 8: 00, 16: 00, and 2: 00, and Cry 1 at 7: 00, 8: 00, and 10: 00 compared to the three-meal group (P<0.05). Conversely, significantly lower expressions of Bmal 1 at 10: 00, 12: 00, and 13: 00, and Cry 1 at 20: 00 and 2: 00 were observed in the six-meal group (P<0.05). No significant differences in the mRNA expressions of Ppar α and Sirt 1 were detected between groups at any time points (P>0.05) .
Conclusion Frequent six-meal consumption elevates insulin and glucose levels, disrupts metabolic homeostasis, and alters circadian clock gene expression in phase and amplitude. These changes induce glucose metabolism dysregulation, leading to circadian rhythm disruption.
