Long-term fasting and its influence on inflammatory biomarkers: A comprehensive scoping review

Despite the rising popularity of prolonged fasting, its biological effects and potential risks remain unclear, with claims suggesting it reduces inflammation. This systematic scoping review examines the impact of prolonged fasting (≥48 h) on key inflammatory biomarkers: C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α).

Following PRISMA-ScR guidelines, a comprehensive search of PubMed, Medline (Ovid), Web of Science, Embase (Classic and Embase), and Scopus was conducted for studies published up to August 2024. Eligible studies were peer-reviewed human clinical trials that investigated prolonged fasting's effects on inflammatory markers.

Following a systematic search across multiple databases, 14 studies met the inclusion criteria. Contrary to popular belief, the majority of studies reported either no change or an increase in inflammatory biomarkers during prolonged fasting. CRP levels frequently rose-often significantly-during fasting periods, particularly in individuals with overweight or obesity. Some studies also reported increases in TNF-α and IL-6, though results were less consistent. Importantly, several studies showed a reduction or normalization of CRP levels after refeeding, suggesting that the inflammatory response to fasting may be transient or adaptive. These discrepancies may be due to differences in fasting duration, participant characteristics, and study design.

This review finds limited and inconsistent evidence on prolonged fasting's effects on inflammation, with varied study designs and lack of standard protocols. Overall, prolonged fasting appears to lead to an increase in inflammation that may represent an adaptive mechanism. Future research, particularly randomized controlled trials, is needed to assess the long-term impacts of fasting on inflammation and metabolic diseases across different populations.