Effectiveness of Intermittent Fasting Interventions on Glycemic Control in Type 2 Diabetes: Systematic Review of Randomized Controlled Trials

Abstract

Background: Intermittent fasting (IF) has emerged as a popular dietary strategy for type 2 diabetes (T2DM) management, yet its comparative efficacy and long-term sustainability remain areas of active investigation. This systematic review synthesizes current evidence on the effectiveness of various IF regimens on glycemic control in adults with T2DM. Methods: A systematic search of PubMed/MEDLINE, Embase, CENTRAL, Web of Science, and Scopus was conducted. Randomized controlled trials (RCTs) comparing IF types to standard care or continuous energy restriction (CER) in adults with T2DM were included. The primary outcome was change in HbA1c; secondary outcomes included fasting plasma glucose (FPG), insulin requirements, and hypoglycemia. Results: Fifteen reports of 12 unique RCTs were included. IF consistently improved short-term glycemic control. Time-restricted feeding (TRF) with a 10-hour window showed large HbA1c reductions (-1.54%). The 5:2 diet was superior to lifestyle control in newly diagnosed patients but non-inferior to CER in longer trials. In insulin-treated patients, IF protocols yielded significant HbA1c reductions and insulin dose sparing without severe hypoglycemia. However, long-term sustainability was variable, with glycemic benefits often attenuating despite maintained weight loss, except in highly structured programs like IF-based medical nutrition therapy, which achieved 47.2% remission at one year. Conclusion: IF is an effective short-term intervention for improving glycemic control across the T2DM spectrum, demonstrating particular promise in insulin-treated populations and with TRF protocols. Its clinical utility is limited by challenges in maintaining long-term adherence and glycemic benefits, underscoring the need for integrated behavioral and clinical support systems.