Introduction: Lifestyle factors are expected to contribute to the persistence and burden of low-back pain (LBP). However, there are no systematic reviews on the (cost-)effectiveness of combined lifestyle interventions for overweight or obese people with LBP. Aim: To assess whether combined lifestyle interventions are (cost-)effective for people with persistent LBP who are overweight or obese, based on a systematic review. Design: Systematic review. Method: PubMed, Cochrane, Embase, CINAHL, PsycINFO and the Wiley/Cochrane Library were searched from database inception till January 6th 2023. Two independent reviewers performed study selection, data-extraction and risk of bias scoring using the Cochrane RoB tool 2 and/or the Consensus Health Economic Criteria list. GRADE was used to assess the level of certainty of the evidence. Results: In total 2510 records were screened, and 4 studies on 3 original RCTs with 216 participants were included. Low certainty evidence (1 study) showed that combined lifestyle interventions were not superior to usual care for physical functioning, pain and lifestyle outcomes. Compared to usual care, moderate certainty evidence showed that healthcare (-$292, 95%CI: 872; −33), medication (-$30, 95% CI -65; −4) and absenteeism costs (-$1000, 95%CI: 3573; −210) were lower for the combined lifestyle interventions. Conclusion: There is low certainty evidence from 3 studies with predominantly small sample sizes, short follow-up and low intervention adherence that combined lifestyle interventions are not superior to physical functioning, pain and lifestyle outcomes compared to usual care, but are likely to be cost-effective.