The effects of time-restricted eating versus habitual diet on inflammatory cytokines and adipokines in the general adult population: a systematic review with meta-analysis

Background: Time-restricted eating (TRE) may facilitate weight loss, but its impact on inflammation remains unclear. Chronic inflammation can detrimentally increase risk of obesity-associated comorbidities. Objectives: The aim of this systematic review was to synthesize and determine the effects of TRE on cytokine and adipokines (C-reactive protein [CRP], TNF alpha [TNF-alpha], interleukin-6 [IL-6], leptin, and adiponectin) in adults. Methods: PubMed, Scopus, Cochrane CENTRAL, and Web of Science were systematically searched for randomized controlled trials (RCTs) and non-RCTs to determine the effects of TRE on cytokines and adipokines in adults up to 23 June, 2023. Risk of bias was assessed using risk of Bias 2 tool for RCTs and the ROBINS-I for non-RCTs. The standardized mean differences (SMDs) and their 95% confidence intervals (CIs) were estimated with the DerSimonian-Laird method through random-effect models. The PRISMA recommendations were followed. Results: A total of 25 studies (13 RCTs, 12 non-RCTs) involving 936 participants were included. The pooled SMD for the effect of TRE compared with the control group on cytokines and adipokines was -0.11 (95% CI: -0.33, 0.12; I2 = 19.7%; n = 10 comparisons) for CRP; -0.25 (95% CI: -0.47, -0.03; I2 = 0%; n = 11 comparisons) for TNF-alpha; -0.09 (95% CI: -0.39, 0.21; I2 = 16.4%; n = 8 comparisons) for IL-6; -0.81 (95% CI: -1.37, -0.24; I2 = 65.3%; n = 5 comparisons) for leptin; and 0.07 (95% CI: -0.40, 0.54; I2 = 56.9%; n = 6 comparisons) for adiponectin. Conclusions: Time-restricted eating may be an effective approach to reduce TNF-alpha and leptin levels in the general adult population. This review was registered at PROSPERO as CRD42022358162.