Muscle Mass

Definition

Skeletal muscle mass is the total amount of muscle tissue in the body, representing 40-50% of body weight in healthy adults and the primary determinant of basal metabolism.

How it works

Skeletal muscle consumes 13 kcal/kg/day at rest (vs 4 kcal for fat). With age, muscle loss (sarcopenia) begins at 30 years (-0.5-1%/year) and accelerates after 50 years, associated with frailty, falls, and premature death. Insulin resistance is negatively correlated with muscle mass.

Role

Produce strength, maintain posture, regulate blood sugar, determine basal metabolism.

Examples

• 75kg man: approximately 30-35kg of muscle, after 60 years without training: -5kg of muscle/decade

Recommendations

Resistance exercise 2-3 times/week and protein intake 1.2-1.6g/kg/day to preserve muscle mass.

Key takeaway

Preserving muscle mass with age is the most valuable health investment.

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