Dose-ranging pilot randomized trial of amino acid mixture combined with physical activity promotion for reducing abdominal fat in overweight adults.

Objective: The objective of this study was to determine the effective dose of an amino acid mixture comprising arginine, alanine, and phenylalanine combined with physical activity promotion in reducing abdominal fat among overweight adults.

Methods: A 12-week randomized, double-blind, placebo-controlled, dose-ranging, pilot trial was conducted in Mito, Japan, from January through April 2016, and the data were analyzed from May through November 2016. The study participants were 35 overweight adults, aged 20-64 years, with no regular exercise habit. Participants were randomly assigned to high-dose (3,000 mg/d, n=9), medium-dose (1,500 mg/d, n=9), low-dose (750 mg/d, n=8), or placebo (0 mg/d, n=9) groups, and the test beverage containing the amino acid mixture or placebo was administered for 12 weeks. All participants maintained a physically active lifestyle during the study period through monthly physical activity promotion sessions and smartphone-based self-monitoring with wearable trackers. Primary outcomes were changes in abdominal total, subcutaneous, and visceral fat areas, assessed by computed tomography.

Results: Of the 35 enrolled participants, 32 completed the 12-week follow-up visit. The intention-to-treat analysis revealed that the changes in abdominal total fat area were -14.6 cm (95% confidence interval [CI], -39.6 cm to 10.4 cm), -25.3 cm (95% CI, -71.0 cm to 20.3 cm), -23.2 cm (95% CI, -48.0 cm to 1.6 cm), and -12.5 cm (95% CI, -29.1 cm to 4.0 cm) in the high-dose, medium-dose, low-dose, and placebo groups, respectively. Similar results were obtained for visceral and subcutaneous fat areas. No study-related adverse events were reported.

Conclusion: Compared with placebo, a medium or low dose of the amino acid mixture may facilitate abdominal fat reduction among overweight adults. A larger randomized trial with sufficient statistical power should be implemented to validate the effectiveness of this supplement.