Effects of feeding schedule changes on the circadian phase of the cardiac autonomic nervous system and serum lipid levels

The purpose of this study was to investigate whether scheduling meals earlier in the day affects the circadian phase of the cardiac autonomic nervous system as assessed by heart rate variability (HRV) and serum lipid levels. Healthy men aged 21.4 +/- A 0.5 years (n = 14) with a habit of regularly skipping breakfast participated in this parallel trial involving altered feeding schedules. Participants in the early mealtime group (EM group, n = 8) were asked to eat three meals at 8:00, 13:00, and 18:00, and the control group (n = 6) ate at 13:00, 18:00, and 23:00 for 2 weeks. On the measurement day before and after intervention, fasting blood samples and 24-h electrocardiograph recordings were collected. Spectral analysis was used for approximate 10-min HRV segments. Low frequency (LF) power, high frequency (HF) power, and the ratio of HF to total power (%HF) were calculated to assess sympathovagal balance. Acrophases of the circadian rhythm of HRV variables were obtained by nonlinear least squares regression. Triglyceride and total and LDL cholesterol levels were significantly decreased in the EM group when compared with the control group (p = 0.035, 0.008, and 0.004, respectively). Acrophases for HRV variables were advanced in the EM group and their difference between before and after the intervention in LF power (-3.2 +/- A 1.2 h) and %HF (-1.2 +/- A 0.5 h) reached significant level, respectively (p < 0.05). Timing of meals was a key factor in regulating circadian phases of the cardiac autonomic nervous system and lipid metabolism.