Anabolic Resistance: Age-Related Decline in Muscle Protein Synthesis Response
research · Muscle protein turnover studies in young vs. older adults (2022)
Aging reduces the ability of skeletal muscle to respond to anabolic stimuli such as dietary protein and resistance exercise, a phenomenon termed anabolic resistance. This makes it harder for older adults to maintain and build muscle.
Core Concepts
The Problem
Anabolic resistance drives age-related muscle loss (sarcopenia), contributing to weakness, metabolic dysfunction, and loss of independence.
The Claim
Older adults exhibit a blunted muscle protein synthetic response to protein ingestion and exercise. To overcome this, they need higher protein doses, richer in leucine, combined with regular resistance training.
Key Evidence
- •Stable isotope studies show that older muscles have reduced phosphorylation of key anabolic signaling molecules like mTORC1.
- •Clinical trials demonstrate that older adults require ~0.4 g/kg of high-quality protein per meal to maximize synthesis, compared to ~0.24 g/kg in young adults.
Practical Implication
Nutritional strategies for aging populations must account for anabolic resistance by increasing both total protein intake and protein quality per meal.
Nuance & Limits
Anabolic resistance can be partially overcome by exercise; even a single bout of resistance training sensitizes muscle to protein for up to 24–48 hours. Inactivity accelerates resistance.
Source Material
Citation Density
Foundational concept in muscle biology and gerontology
Related Ideas
The protein recommendations are directly informed by anabolic resistance; they are two sides of the same coin.
Gaps
- ⚠ Molecular mechanisms of anabolic resistance (e.g., role of inflammation, capillarization) are still being elucidated.
- ⚠ Individual variation in degree of resistance is not well quantified.
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