Effects of Protein yogurts vs. Whey protein on body composition, strength, and gut microbiome changes in untrained older adults during 8 weeks of supervised strength training: a randomized trial.

Methods Seventeen untrained adults (60–70 years) were randomized to either consume WP (25 g) or PY (24.5 g) along with an 8-week supervised ST program (3 sessions/week). Initial and final assessments included body composition (BIA), strength (10RM, isokinetic torque, handgrip), gait speed, resting metabolic rate, and gut microbiome (16S rRNA sequencing). Data were analyzed using repeated-measures ANOVA and diversity metrics. Results Both groups increased skeletal muscle mass (WP: +0.47 kg; PY: +0.50 kg) and improved strength and gait speed (p < 0.01), with no between-group differences. Fat mass decreased only in WP (p = 0.02), while resting metabolic rate increased in PY (p = 0.03). Microbiome analysis revealed distinct shifts: WP increased the Firmicutes/Bacteroidota ratio and enriched Subdoligranulum , whereas PY enhanced alpha diversity and increased the abundance of Coprococcus . Functional pathway predictions indicated differential enrichment in metabolic and signaling processes. Conclusion High-protein yogurt and whey protein similarly improve muscle mass, strength, and functional capacity during ST, while exerting distinct effects on gut microbiome composition. Yogurt represents a cost-effective alternative to whey protein and may confer additional gut health benefits. Trial registration: Clinicaltrials.gov identifier NCT06412302 . Date of registration 2024-05-14.