Background: Metabolic syndrome (MS) is reportedly associated with high mortality from mostly cardiovascular causes in patients with severe mental disorders (SMD). Lifestyle interventions augment effective management of MS in patients with SMD. The present meta-analysis aims at updating the recent evidence on the effectiveness of lifestyle intervention for MS in patients with SMD. Method: A literature search for English Language publications of randomized controlled trials (RCTs) from 2001 to 2016 comparing lifestyle modification (LM) with treatment as usual (TAU) in the management of MS were identified. Using PRISMA guidelines, 19 RCTs reporting data on 1688 SMD and MS patients and providing data on change in Body Weight, Body Mass Index (BMI) and waist circumference (WC) were included. Using random effects model, standardized mean difference between LM and TAU for the mean baseline-to-endpoint change in body weight, BMI and WC was calculated with a 95% confidence limit, on RevMan 5.3. The study was registered with PROSPERO (CRD42016046847). Results: LM had significantly superior efficacy in the reducing weight (−0.64, 95% CI −0.89, −0.39, Z = 5.03, overall effect p b 0.00001), BMI (−0.68, 95% CI −1.01, −0.35, Z = 4.05, overall effect p b 0.0001), and WC (−0.60, 95% CI −1.17, −0.03, Z = 2.06; overall effect p = 0.04), compared to TAU. LM was significantly more effective than TAU even in short duration (p = 0.0001) and irrespective of the treatment setting. Conclusion: Interventions targeting LM in persons with SMD and MS are effective in reducing body weight, BMI and WC. It must be routinely recommended to all patients with SMD, ideally during commencement stage of second generation antipsychotic treatment