BACKGROUND: Intermittent fasting is an annual religious practice of Muslims worldwide, which affects the physiology of the body due to lifestyle alterations. This study aimed to evaluate the effect of Ramadan fasting on the HRV, an indirect measure of cardiac sympathetic stress. METHODS: This study included 80 healthy Lebanese females (aged 18-25 years old) monitored for 24 h when following normal routine; 38 and 42 females were enrolled before and during Ramadan, respectively. RESULTS: Our results reveal no effect of fasting on HRV; there was insignificant change in HRV between the first and last weeks of Ramadan (P > 0.05). Morning fasting was significantly the least stressful period (lowest HR, P < 0.001), with lower HR compared with non-fasting day (P < 0.001). Therefore, Ramadan fasting does not alter the autonomic nervous activity of the heart, neither HRV levels. CONCLUSIONS: This may imply that intermittent fasting is a risk-free practice, which does not interfere with the cardiac autonomic nervous system function.