Intermittent Fasting and Time-Restricted Eating for Metabolic Syndrome: A Comprehensive Narrative Review of Mechanisms and Clinical Evidence

Abstract

Background: Metabolic syndrome (MetS) is a clustering of abdominal obesity, hypertension, dyslipidaemia, and dysglycaemia is now affects an estimated 1.54 billion adults worldwide and continues to rise across countries of all income levels. Intermittent fasting (IF) and time-restricted eating (TRE), which confine intake to defined fasting-feeding cycles rather than continuous caloric reduction, have emerged as popular alternatives to continuous energy restriction (CER) for MetS prevention and management. This review synthesizes mechanistic and clinical trial evidence on the principal IF protocols alternate-day fasting (ADF), the 5:2 diet, and TRE and evaluates their efficacy and safety in adults with or at risk of metabolic syndrome.

Methods: A non-systematic search was conducted in PubMed, Embase, and the Cochrane Library for landmark randomized controlled trials (RCTs), meta-analyses, umbrella reviews, and mechanistic studies published between 2016 and 2026.

Results: Fasting periods sufficient to deplete hepatic glycogen trigger a metabolic switch from glucose- to ketone-based metabolism, activating cellular stress-resistance and autophagy pathways. Across more than fifteen RCTs and several meta-analyses, IF and TRE produce modest reductions in body weight (1-8%), improved insulin sensitivity, and favourable changes in blood pressure and lipids—generally comparable to, but not consistently superior to, matched continuous energy restriction. One isocaloric trial showed fasting itself, independent of net energy restriction, can confer modest benefit.

Conclusion: IF and TRE are effective, safe, and flexible strategies for improving cardiometabolic risk factors in adults with metabolic syndrome, offering an evidence-based alternative to caloric restriction, though individualization and longer-term outcome data remain needed.