Randomized trial of amino acid mixture combined with physical activity promotion for abdominal fat reduction in overweight adults.

Purpose: The purpose of this study was to test the efficacy of arginine, alanine, and phenylalanine mixture (A-mix) ingestion at 1,500 mg/day in combination with the promotion of physical activity for abdominal fat reduction in overweight adults.

Methods: A placebo-controlled, double-blind, parallel-group, randomized trial for 12 weeks combined with a 4-week follow-up period was conducted at a single center in Minato-ku, Tokyo, Japan, between December 2016 and May 2017. Data were analyzed between June and August 2017. The study participants were 200 overweight adults within the age range of 20-64 years. The participants were randomly assigned to the A-mix group (n=100) or a placebo group (n=100) and were administered 500 mL of test beverage containing 1,500 or 0 mg of A-mix, respectively, for 12 weeks. All participants maintained a physically active lifestyle between week 0 and week 12 through monthly sessions of physical activity. The primary outcomes were the 12-week changes in the abdominal total, subcutaneous, and visceral fat areas, as assessed by computed tomography.

Results: Of the 200 enrolled participants, 199 (99%) accomplished the 12-week intervention and 4-week follow-up period. The per-protocol-based analysis for 194 participants demonstrated that the abdominal total fat area decreased significantly in the A-mix group compared with that in the placebo group (difference, 10.0 cm2 ; 95% confidence interval [CI]: 0.4-19.6 cm2 ; P =0.041). Comparable outcomes were obtained for the abdominal subcutaneous fat area (difference, 7.4 cm2 ; 95% CI: 0.1-14.7 cm2 ; P =0.047). No study-related unfavorable events occurred.

Conclusion: A-mix supplementation in combination with physical activity promotion facilitated abdominal fat reduction in overweight adults.