Impact of Intermittent Fasting on Autonomic Nervous System Regulation and Heart Rate Variability

Background: Intermittent fasting (IF) has emerged as a dietary approach with potential benefits beyond weight reduction, particularly in modulating the autonomic nervous system (ANS) and cardiovascular health. Heart rate variability (HRV) serves as a non-invasive marker of ANS regulation, reflecting sympathovagal balance. However, evidence on the impact of IF on HRV in the Indian population remains limited. Objective: To evaluate the effects of intermittent fasting on autonomic nervous system regulation and HRV among adults attending the general outpatient department (OPD) at Jalpaiguri Government Medical College. Methods: A prospective observational study was conducted from January to December 2023, including 100 adult participants (aged 20–55 years) who voluntarily adopted intermittent fasting (16:8 protocol, fasting 16 hours/day, eating within an 8-hour window) for at least 12 weeks. Baseline clinical and demographic data were collected. HRV was assessed using 5-minute resting ECG recordings analyzed for time-domain and frequency-domain parameters at baseline and after 12 weeks of adherence. Statistical comparisons were performed using paired t-test/Wilcoxon signed-rank test, with p <0.05 considered significant. Results: Significant improvements in HRV indices were observed after 12 weeks of IF. Mean SDNN increased from 36.2 ± 10.1 ms to 49.5 ± 12.4 ms (p <0.001). RMSSD improved from 25.7 ± 8.3 ms to 38.9 ± 9.1 ms (p <0.001). In the frequency domain, HF power (parasympathetic activity) rose by 42%, while LF/HF ratio (sympathovagal balance) decreased from 2.9 ± 0.7 to 1.8 ± 0.5 (p <0.01). Subjective well-being and sleep [10,16] quality also improved in 68% of participants. Conclusion: Intermittent fasting favorably modulates autonomic regulation, with enhanced parasympathetic activity and improved sympathovagal balance as evidenced by HRV indices. These findings suggest that IF may serve as a non-pharmacological intervention for cardiovascular risk reduction. Larger multicenter trials are warranted to generalize these outcomes.