Backgrounds <p>A growing number of studies have shown that bariatric surgery can cause changes in the body composition of patients. This meta-analysis aims to reveal changes in skeletal muscle mass 1&#xa0;year after bariatric surgery and analyze the causes of changes in skeletal muscle in postoperative patients, to provide a more comprehensive clinical basis for preserving muscle mass in patients.</p> Methods <p>We systematically searched PubMed, Embase, Web of Science, and Cochrane databases, and included six studies. The search time limit was from establishing the databases to October 10, 2024. Data on weight, BMI, and skeletal muscle mass at 1-year follow-up after bariatric surgery were collected. Meta-analysis was conducted using Review Manager 5.2 statistical software.</p> Results <p>After analysis, the skeletal muscle mass decreased significantly from preoperative to postoperative 3&#xa0;months, and the difference was statistically significant ([WMD = 3.30&#xa0;kg, 95%CI (2.18, 4.41)], <i>P</i> &lt; 0.00001). Skeletal muscle mass was not statistically significant from 3 to 6&#xa0;months after surgery and 6 to 12&#xa0;months after surgery.</p> Conclusion <p>The skeletal muscle mass of patients after bariatric surgery showed a downward trend within 1&#xa0;year after surgery, especially in the first 3&#xa0;months.</p>