Background Large-scale empirical and observational studies confirm the safety and efficacy of short-term intermittent fasting; however, prolonged fasting (fasting for more than two days or more) is not well studied. This study investigated the safety, physiological, and psychological effects of a medically supervised fasting (MSF) regimen on healthy volunteers. Methods In this observational study, 117 female participants with an average age of 21.02 (± 1.45) years underwent 10 days of medically supervised fasting. Daily symptom scores and 24-hour food recalls were collected, along with serum levels of vitamin D and calcium, a complete blood count, anthropometric measurements, quality of life (QoL), and subjective mood, anxiety, and depression scores, at the baseline and at the end of fasting. Results Compared to baseline, significant improvements were observed in vitamin D levels (z = -8.79, p = 0.000), calcium levels (z = -4.08, p = 0.000), red blood cell count (z = -4.61, p = 0.000), and hemoglobin levels (z = -5.57, p = 0.00). Improvements were observed in physical QOL (t (116) = -4.51, p = 0.000); psychological QOL (t (116) = -4.70, p = 0.000); and social QOL (t (116) = -2.68, p = 0.008). We also observed significant reductions in body weight (55.83 (±11.38), 52.99 (±10.94); p = 0.00) and other anthropometric measures. More than 80% (n = 94) experienced at least one symptom associated with fasting. The symptoms associated with fasting changed significantly (p<0.05), with most symptoms peaking from day 3 to day 7 of fasting with remission from day 8 onwards. Conclusion Our findings suggest that MSF is associated with significant improvements in physiological and psychological variables. The symptoms associated with MSF are to be considered in clinical decision-making, and follow-up of patients on fasting therapy, particularly during the peaking of symptoms, may be warranted.
Keywords: blood cell count; calorie restriction; fasting; lifestyle; nutrition therapy; vitamin d.
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