BACKGROUND:Metabolic syndrome is characterised by a clustering of metabolic risk factors including abdominal obesity, raised triglycerides, lowered HDL cholesterol, hypertension and impaired glucose tolerance. Multifaceted lifestyle interventions including diet and exercise are recommended as the first-line treatment for the metabolic syndrome. OBJECTIVE:To investigate the effects of lifestyle interventions that include both diet interventions and supervised exercise on outcomes for people with metabolic syndrome. METHODS:A systematic review and meta-regression was conducted. PubMed, EMBASE, MEDLINE and CINAHL were searched from the earliest date possible until November 2018 to identify randomised controlled trials examining the effects of lifestyle interventions compared to usual care on patient health outcomes and components of metabolic syndrome. Post-intervention means and standard deviations were pooled using inverse variance methods and random-effects models to calculate mean differences (MD), standardised mean differences (SMD) and 95% confidence intervals (CI). RESULTS:Searching identified 2598 articles, of which 15 articles reporting data from 10 trials, with 1160 participants were included in this review. Compared to usual care, supervised lifestyle intervention demonstrated significant improvements in all but one of the components of metabolic syndrome. Reductions were seen in waist circumference (-4.9 cm, 95%CI -8.0 to -1.7), systolic blood pressure (-6.5 mmHg, 95%CI -10.7 to -2.3), diastolic blood pressure (-1.9 mmHg, 95%CI -3.6 to -0.2), triglycerides (SMD -0.46, 95%CI -0.88 to -0.04) and fasting glucose (SMD -0.68, 95%CI -1.20 to -0.15). Prevalence of metabolic syndrome was reduced by 39% in intervention group participants compared to control group participants (Risk Ratio 0.61, 95%CI 0.38 to 0.96). Improvements in quality of life were not statistically significant. CONCLUSION:There is low to moderate quality evidence that supervised multifaceted lifestyle intervention improves multiple risk factors of metabolic syndrome, as well as reducing prevalence of the disease. Health services should consider implementing lifestyle intervention programs for people with metabolic syndrome to improve health outcomes and prevent progression to chronic disease.