The effects of protein supplementation on body composition after bariatric surgery: a systematic review and meta‐analysis of randomized controlled trials

OBJECTIVE: We aimed to explore the effect of protein supplementation on anthropometric measures and body composition in patients after metabolic bariatric surgery (MBS). METHODS: We performed a systematic search up to January 2024 including randomized controlled trials investigating the effects of protein or amino acid supplementation on the body composition of patients who underwent MBS. The overall effect was presented as the weighted mean difference (WMD) at a 95% CI. RESULTS: Ten trials were included in this meta-analysis. Our results indicate that there was a statistically greater change in weight (WMD, -1.31 kg, 95% CI: -1.93 to -0.69, p < 0.001; Grading of Recommendations Assessment, Development, and Evaluation [GRADE] = moderate), muscle mass (WMD, 1.33 kg, 95% CI: 0.1 to 2.57, p = 0.035; GRADE = low), fat-free mass (WMD, 1.74 kg, 95% CI: 0.46 to 3.01, p = 0.01; GRADE = low), and fat mass (WMD, -3.91 kg, 95% CI: -4.10 to -0.59, p = 0.01; GRADE = low) in the protein group compared to the control group. However, protein supplementation did not significantly change BMI and lean body mass. CONCLUSIONS: Based on moderate- to low-certainty evidence, our findings suggest that although protein supplementation may improve weight and some body composition metrics, it does not influence overall BMI and lean body mass. More research is needed to recommend protein supplementation after MBS.