Figure 1.

Carbohydrate and fat intake effects on heart rate (HR) and HR variability parameters: 12-h-average analysis.

(a) The HRs of the rats in the standard-diet period are not significantly different from those in the experimental period during the dark or light periods. However, the HRs are significantly higher during the dark period than during the light period on days one and two for all types of diet (P < .01).

(b) The high frequency (HF) power is significantly higher in the carb-diet period than in the standard-diet period during the dark period on day one (P < .05) but not significantly different between the dark and light periods in all diet periods.

(c) The low frequency (LF) power is not significantly different between the standard- and experimental-diet periods and between the dark and light periods.

(d) The LF/HF ratio is significantly higher in the fat-diet period than in the standard-diet period during the dark period on day one (P < .05).

The HR and HRV parameters (HF, LF, LF/HF) are averaged for 2 days before starting the experimental diets. The HR and HRV parameters (HF, LF, LF/HF) during 12 hours of darkness and 12 hours of light on day one and day two are presented here.

Carb: carbohydrate, LF/HF: ratio of LF to HF, *P < .05, **P < .01