A nonrandomized controlled clinical pilot trial on 8 wk of intermittent fasting (24 h/wk).

ABSTRACT

OBJECTIVE: The aim of the study was to evaluate whether intermittent fasting (IF) is an effective preventive measure, and whether it is feasible for healthy volunteers under every day conditions. METHODS: A nonrandomized controlled clinical trial on IF was performed with healthy volunteers over a period of 8 wk, and a subsequent 4-mo follow-up. Outcomes were assessed at baseline, after 8 wk, and after 6 mo. Volunteers who were not interested in fasting served as a control group. Participants in the fasting group were asked to continue their regular nutritional habits on the nonfasting days, whereas the control group maintained their habitual nutrition throughout the whole period. Outcomes included changes of metabolic parameters (insulin, glucose, insulin resistance, insulin-like growth factor-1, brain-derived neurotropic factor, lipids, liver enzymes, hemoglobin A1c) and coagulation markers; bioelectrical impedance analysis; body mass index; abdominal girth; blood pressure; general quality of life (five-item World Health Organization Well-Being Index [WHO-5] questionnaire), as well as mood and anxiety (Hospital Anxiety and Depression Scale [HADS], Profile of Mood States, Flourishing-Scale, visual analog scale, Likert scales). The intervention consisted of a fasting day, which was repeated every week for 8 wk, with abstinence from solid food between 0000 and 2359 at minimum and a maximum caloric intake of 300 kcal on each fasting day. A per-protocol analysis was performed. P < 0.05 was considered significant. RESULTS: Thirty-six volunteers were included; 22 allocated themselves to the fasting group, and 14 to the control group. Thirty-three data sets were included in the final analysis. Although significant in-group changes were observed in both groups for a number of outcomes after 8 wk and 6 mo, no significant between-group differences were observed for any outcome other than overall body fat mass after 8 wk as well as for the HADS total score and the WHO-5 total score after 6 mo, all in favor of the fasting group. However, none of the between-group differences were clinically relevant. CONCLUSIONS: We did not find any clinically relevant differences between groups in this controlled clinical pilot trial of 8 wk of IF in healthy volunteers. Further clinical research in this field is warranted to further analyze mechanisms and effects of IF.