Aim To analyse the effect of fasting on the retinal vascular plexus and choriocapillaris structures in healthy subjects via Optical Coherence Tomography Angiography (OCTA). Methods In this prospective study, OCTA scans of 98 eyes in 49 healthy subjects were compared in fasting and non-fasting period. All cases had a full ophthalmological examination, with OCTA parameters measured, including superficial flow area (SCP) (mm 2), deep flow area (DCP) (mm 2), choriocapillaris flow area (CC) (mm 2), superficial and deep vascular density (SVD and DVD, respectively) (%), superficial foveal avascular zone area (FAZs) (mm 2), deep foveal avascular zone area (FAZd) (mm 2), subfoveal choroidal thickness (SFCT) (μm) and central macular thickness (CMT) (μm). Results The mean SCP, DCP and CC flow area values were induced to be significantly lower in a fasting than a non-fasting period (p<0.001, p<0.001, p=0.049, respectively). The mean VD in a fasting period was statistically significantly lower than in a non-fasting period at the SCP level (p=0.009). No statistically significant difference was found between the two periods in respect to DVD, FAZd and CMT (p=0.068, p=0.653 and p=0.531, respectively); however, FAZs were significantly lower in a non-fasting than fasting period (p=0.038). The SFCT was determined to be statistically significant and thicker during a fasting period (p<0.001). Conclusion The current study documented several physiological changes in a fasting period, such as changes in SCP, DCP, CC flow, SVD and DVD, via OCTA.