Background
Acupuncture has shown potential therapeutic benefits for individuals with simple obesity. However, some researchers argue that some of the effectiveness of acupuncture may be due to the placebo response.
Objective
To understand the placebo response of acupuncture treatment in simple obesity, a systematic review and meta-analysis was designed based on the comparison between sham acupuncture before and after treatment.
Search strategy
Eight databases (PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure, Wanfang Database, China Biology Medicine Database, and Chinese Scientific Journals Database) were searched from inception to August 1, 2023. The MeSH search terms comprised obesity and acupuncture.
Inclusion criteria
Randomized controlled trials (RCTs) using sham or placebo acupuncture as a control in treating obesity were enrolled.
Data extraction and analysis
Two researchers independently extracted data, and the results were cross-checked after completion. Each RCT’s detailed sham/placebo acupuncture treatment protocol was assessed according to the SHam Acupuncture REporting guidelines. The revised Cochrane risk-of-bias tool for randomized trials and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system were used to determine the risk of bias and quality of evidence, respectively. Body mass index (BMI) was defined as the primary outcome. Anthropometric parameters and laboratory test parameters related to obesity were defined as secondary outcomes. We used standardized mean difference (SMD) with 95% confidence interval (CI) to calculate treatment effects of outcomes.
Results
Fifteen RCTs with a total of 1250 patients were included. The BMI significantly decreased after treatment in the sham acupuncture group compared to baseline (SMD 0.37, 95% CI 0.09–0.66; I² = 81%, random model; P < 0.01). Treatment duration (P = 0.02) and other interventions significantly impacted the placebo response rate (P = 0.00).
Conclusion
The placebo response of sham acupuncture was strong in the RCTs for simple obesity, and the effect sizes differed between various outcomes. The treatment duration and other interventions emerged as potential influencing factors for the placebo response of sham acupuncture.

Key words: Simple obesity, Overweight, Sham acupuncture, Placebo response, Meta-analysis