The Effects of Combined Exercise with Citrulline Supplementation on Body Composition and Lower Limb Function of Overweight Older Adults: A Systematic Review and Meta-Analysis

The combined exercise with citrulline (CIT) supplementation is a potential adjuvant treatment approach to address the declining body composition and lower limb function of overweight older adults. However, research on this approach is limited. Thus, this study performed a meta-analysis review to explore the effects of combined exercise with CIT supplementation on body composition and lower limb function among overweight older adults. The search strategy and manuscript development of this study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Eligible studies were first searched through four databases (Web of Science, Scopus, PubMed, and EBSCO) from January 2003 until April 2023, followed by screening. The main inclusion criteria for the article selection are as follows: 1) Randomized Controlled Trial studies; 2) Participants aged over 55; 3) Studies involved exercise with CIT supplementation for the experimental group and exercise with Placebo (PLA) supplementation for the control group; 4) Body composition and lower limb function were measured at pre-and post intervention. Subsequently, the Cochrane risk of bias assessment tool was utilized to evaluate the selected studies' quality. The Standardized Mean Difference (SMD) was chosen as the suitable effect scale index, and the mean differences of the data from the selected articles were analyzed using Revman 5.4 software with a 95% Confidence Interval (CI). A total of seven studies fulfilled the inclusion criteria and were selected for the meta-analysis. The included studies involved 105 males and 198 females, where 157 belonged to the PLA group and 146 from the CIT group. Significant improvements were observed among overweight older adults with CIT supplementation in 6-Minute Walking Test (6MWT) (P = 0.04, I2 = 4%), SMD (95% CI) =-0.28 (-0.54,-0.01), and Lower Limb Strength (LLS) (P < 0.01, I2 = 30%), SMD (95% CI) = 0.38 (-0.65,-0.12) compared to those with PLA supplementation. Combined exercise with CIT supplementation could be an effective non-pharmaceutical intervention to improve the physical function of overweight older adults by increasing their muscle strength.