Age-related anabolic resistance and post-absorptive muscle protein synthesis: integrative evidence from a systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of non-randomized comparative physiological studies (young vs. older cohorts).
PubMed 42326998 · doi:10.3389/fphys.2026.1740284
What was done
A systematic literature search was conducted through November 2025 across major databases to identify studies comparing muscle protein synthesis (MPS) between young (18–35 years) and older (≥60 years) healthy adults using stable isotope tracer techniques under controlled conditions. Random-effects meta-analyses were performed for post-absorptive and post-prandial conditions. Post-exercise and combined post-prandial/-exercise outcomes were synthesized qualitatively due to methodological heterogeneity. Risk of bias was assessed using the ROBINS-I tool.
What was found
Forty-six studies with 1,280 participants (700 older, 580 young) met inclusion criteria: - Post-absorptive MPS was significantly lower in older adults compared with younger adults (SMD = -0.167; 95% CI: -0.313 to -0.021; p = 0.025; I² = 18.4%). - Post-prandial MPS was significantly reduced in older adults (SMD = -0.348; 95% CI: -0.627 to -0.070; p = 0.014; I² = 83.4%). - Post-exercise MPS showed no significant age-related difference in 5 out of 8 studies. - Combined post-prandial/-exercise MPS showed no significant age-related difference in 7 out of 9 studies. - Overall risk of bias was rated low to moderate.
Why it matters
This meta-analysis demonstrates modest reductions in basal and feeding-induced muscle protein synthesis with age, but confirms that muscle anabolic potential remains intact following exercise stimuli.
Limits
High heterogeneity was present in the post-prandial analysis (I² = 83.4%). Post-exercise and combined conditions could not be quantitatively meta-analyzed due to methodological variation. Stable isotope tracer protocols were non-standardized across studies, and sex-specific analyses were not available.
Cited by
- supports Aging naturally causes anabolic resistance, making the body lose muscle and absorb and utilize dietary protein less efficiently.