The magnitude and progress of lean body mass, fat‐free mass, and skeletal muscle mass loss following bariatric surgery: A systematic review and meta‐analysis

Summary Postbariatric loss of muscle tissue could negatively affect long‐term health due to its role in various bodily processes, such as metabolism and functional capacity. This meta‐analysis aimed to unravel time‐dependent changes in the magnitude and progress of lean body mass (LBM), fat‐free mass (FFM), and skeletal muscle mass (SMM) loss following bariatric surgery. A systematic literature search was conducted in Pubmed, Embase, and Web of Science. Fifty‐nine studies assessed LBM (n = 37), FFM (n = 20), or SMM (n = 3) preoperatively and ≥1 time points postsurgery. Random‐effects meta‐analyses were performed to determine pooled loss per outcome parameter and follow‐up time point. At 12‐month postsurgery, pooled LBM loss was −8.13 kg [95%CI −9.01; −7.26]. FFM loss and SMM loss were −8.23 kg [95%CI −10.74; −5.73] and −3.18 kg [95%CI −5.64; −0.71], respectively. About 55% of 12‐month LBM loss occurred within 3‐month postsurgery, followed by a more gradual decrease up to 12 months. Similar patterns were seen for FFM and SMM. In conclusion, >8 kg of LBM and FFM loss was observed within 1‐year postsurgery. LBM, FFM, and SMM were predominantly lost within 3‐month postsurgery, highlighting that interventions to mitigate such losses should be implemented perioperatively.