Does muscle mass protect against cardiovascular disease?

Higher skeletal muscle mass is independently associated with lower cardiovascular mortality in multiple large cohort studies, men in the highest quartile of skeletal muscle index (lean mass normalized to body surface area) have approximately 50% lower cardiovascular mortality than those in the lowest quartile, and the mechanism operates through improved insulin sensitivity, higher resting metabolic rate (reducing obesity risk), improved glucose clearance, and anti-inflammatory myokine secretion (Kim et al., J Am Coll Cardiol, 2015).

Skeletal muscle is an endocrine organ, not merely a mechanical one. Contracting muscle secretes myokines, IL-6 (an anti-inflammatory context-dependent signal from exercising muscle, distinct from visceral fat's inflammatory IL-6), irisin, BDNF, and others, that improve insulin sensitivity, reduce inflammation, and appear to suppress tumor growth in epidemiological data. This is the mechanism behind exercise's broad health benefits beyond cardiovascular fitness alone.

Honesty Scale: Solid (1) for skeletal muscle mass as a cardiovascular mortality predictor. Promising (2) for specific myokine mechanisms as the causative pathway.

What to do: Track body composition (lean mass), not just weight. DEXA provides lean mass data. If you do not have access to DEXA, use the sum of chest + arms + legs circumferences as a proxy for muscle mass trend monitoring. A rising lean mass trend alongside stable or declining waist circumference is the body composition direction associated with longevity benefit.

For the full picture, read The Strength/Grip Deep Dive