The effects of protein intake higher than the recommended value on body composition changes after bariatric surgery: A meta-analysis of randomized controlled trials.

BACKGROUND & AIMS: There is a lack of a meta-analysis to comprehensively assess the effectiveness of higher protein intake in addition to the recommended value on body composition post-bariatric surgery. We aimed to perform a meta-analysis of randomized controlled trials to determine the effects of protein intake higher than the recommended value on body composition changes after bariatric surgery.

METHODS: Electronic databases, including Scopus, PubMed/Medline, and Web of Sciences, were searched until July 2023. Studies that assessed the effect of protein intake higher than the recommended value on postoperative body composition, i.e., weight, body mass index (BMI), fat mass (FM), fat-free mass (FFM), percent fat mass (PFM), and percent total weight loss (%TWL), were eligible. For each outcome, the mean and standard deviation (for changes from baseline) were used to synthesize the data.

RESULTS: Eight trials were included in the current study. The results of the meta-analysis indicated protein intake higher than the recommended value after bariatric surgery led to more weight loss by 4.95 kg (95 % CI: -9.41 to -0.49) and FM loss by 7.64 kg (95 % CI: -14.01 to -1.28) compared with the control group. However, it had no significant effects on postoperative changes in BMI, FFM, PFM, or %TWL. There were no significant differences in body composition between protein sources obtained from diet and supplementation. When data was stratified based on the amount of added protein, we found a significant reduction in weight (MD: -7.80 kg; 95 % CI: -14.50 to -1.10) in patients who consumed protein ≥ 40 g/d in addition to the recommended value. Besides, protein intake higher than the recommended value declined FFM loss in patients who underwent laparoscopic sleeve gastrectomy (LSG) (MD: 6.52 kg; 95 % CI: 0.99 to 12.02).

CONCLUSION: The results of the current meta-analysis indicated that protein intake higher than the recommended value might cause greater weight and FM loss after bariatric surgery than a normal protein diet. However, our findings did not support the role of additional protein in the preservation of FFM, except in patients with LSG.