Muscle and longevity - why strength is your most important health asset

Longevity

22 Sept

Written By Cassandra Hilton

Muscle and Longevity — Why Strength Is Your Most Important Health Asset | Cassandra Hilton Naturopath

Cassandra Hilton Clinical Naturopath · BHSc · ATMS Accredited

Muscle and longevity — why strength is your most important health asset

By Cassandra Hilton — Clinical Naturopath, BHSc, ATMS Accredited | Updated August 2026 | 13 min read

Of all the modifiable predictors of longevity, muscle mass and strength are among the most powerful — and the most consistently undervalued in standard medical practice. Grip strength predicts all-cause mortality more accurately than blood pressure. Appendicular muscle mass predicts metabolic disease risk better than BMI. Sarcopenia — the age-related loss of muscle mass and function — is now classified as a disease by the WHO, and for good reason: it is the physiological signature of accelerated biological ageing.

Sarcopenia — what it is and why it matters

Sarcopenia is defined as the progressive, generalised loss of skeletal muscle mass, strength and physical function that occurs with ageing. From the fourth decade, muscle mass declines at approximately 1-2% per year and muscle strength declines at 1.5-5% per year, with the rate accelerating after age 60. By age 80, up to 50% of individuals have clinically significant sarcopenia that impairs functional independence.

The clinical consequences extend far beyond reduced physical capacity. Sarcopenia is independently associated with increased all-cause mortality, cardiovascular disease, type 2 diabetes, cognitive decline, osteoporosis, falls and fractures, and impaired immune function. A landmark 2018 meta-analysis in the Journal of Cachexia, Sarcopenia and Muscle confirmed that low muscle mass was associated with a 2.41-fold increase in all-cause mortality across 58,000 participants — a stronger mortality predictor than the majority of conventional risk factors.

Muscle as an endocrine organ

Skeletal muscle is not merely a contractile tissue — it is the largest endocrine organ in the body, secreting over 600 identified myokines that regulate metabolic, immune, cognitive and cardiovascular function. The myokine profile released during muscle contraction is one of the primary mechanisms by which exercise produces systemic health benefits beyond the metabolic cost of the activity itself.

Irisin, released during aerobic exercise, crosses the blood-brain barrier and stimulates BDNF (brain-derived neurotrophic factor) production — providing a direct biochemical link between muscle activity and cognitive neuroprotection. IL-6 released during exercise has anti-inflammatory effects distinct from the pro-inflammatory IL-6 produced by adipose tissue, stimulating fat oxidation and glucose uptake. IL-15 promotes muscle protein synthesis and has been associated with anti-tumour immune surveillance. The systemic benefits of maintaining muscle mass therefore extend far beyond mechanical function.

Muscle and insulin sensitivity

Skeletal muscle accounts for approximately 80% of insulin-stimulated glucose disposal. A reduction in muscle mass directly reduces the body's glucose buffering capacity — each kilogram of muscle loss reduces insulin sensitivity measurably. This is the mechanistic basis of the strong association between sarcopenia and type 2 diabetes, and explains why resistance training improves glycaemic control comparably to metformin in multiple randomised trials.

The relationship runs in both directions: insulin resistance impairs muscle protein synthesis through reduced IGF-1 signalling, creating a sarcopenia-insulin resistance cycle that accelerates with age. Addressing insulin sensitivity through dietary modification and resistance training simultaneously preserves muscle mass and reduces metabolic disease risk.

Protein — the most underconsumed longevity nutrient

Adequate protein intake is the nutritional prerequisite for muscle protein synthesis. The standard recommended dietary intake of 0.8g/kg body weight is insufficient for muscle preservation in older adults — a 2023 systematic review in Nutrients confirmed that 1.6g/kg is required to optimise muscle protein synthesis in individuals over 60, and 1.8-2.0g/kg in those engaged in regular resistance training.

Protein distribution matters as much as total intake. Muscle protein synthesis is maximised by protein intakes of 30-40g per meal — below this threshold, the leucine-dependent mTOR activation that triggers protein synthesis is not fully achieved. Leucine is the primary anabolic amino acid: a 2.5g leucine threshold appears necessary per meal to maximally stimulate muscle protein synthesis, which is achieved by approximately 30g of high-quality protein from animal or complete plant sources.

Training for longevity — what the evidence supports

Resistance training is the primary intervention for sarcopenia prevention and reversal. The current evidence supports 2-4 sessions per week of progressive resistance training targeting all major muscle groups, with loads of 70-85% of 1RM (one-repetition maximum) producing the greatest hypertrophic response. Older adults respond to resistance training with equivalent relative muscle hypertrophy to younger adults — the rate of adaptation is preserved even into the eighth decade.

The combination of aerobic and resistance exercise produces the greatest longevity benefit — aerobic exercise optimises cardiovascular function, mitochondrial density and autophagic flux while resistance exercise preserves muscle mass, bone density and metabolic health. A 2022 prospective cohort study in the British Journal of Sports Medicine following 116,221 adults confirmed that the combination of aerobic and muscle-strengthening activity was associated with the greatest reduction in all-cause mortality — 41% lower than sedentary controls.

Hormonal drivers of muscle loss

Testosterone, oestrogen, growth hormone and IGF-1 all support muscle protein synthesis, and their decline with age is a primary driver of sarcopenia. In women, the oestrogen withdrawal of menopause produces a period of accelerated muscle loss — oestrogen directly supports satellite cell activation (the muscle stem cells required for repair and hypertrophy) and reduces inflammatory cytokines that impair protein synthesis. In men, testosterone decline — which begins gradually from the third decade — reduces the anabolic signalling that maintains muscle mass. Optimising thyroid function, addressing insulin resistance and managing chronic cortisol elevation are all clinically relevant hormonal interventions for muscle preservation.

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References

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