From around age 30, muscle mass begins a gradual, progressive decline at roughly 3–5% per decade — a process called sarcopenia. By age 70, many sedentary individuals have lost 20–40% of their peak muscle mass, with significant implications for strength, balance, metabolism and independence.
Sarcopenia is not just about physical strength. Muscle is the body's largest metabolic organ — it accounts for the majority of glucose uptake and plays a central role in metabolic regulation. Loss of muscle mass is directly linked to increased type 2 diabetes risk, higher cardiovascular mortality and faster cognitive decline.
Of all age-related changes, muscle loss is the most reversible. A landmark NEJM study found that resistance training in 90-year-olds produced measurable muscle strength gains within 8 weeks. It is never too late to start.
Bone density peaks between ages 25 and 30, then gradually declines. The "bone bank" analogy is useful: the more bone mass you accumulate before 30 through exercise, diet and calcium/vitamin D intake, the more you have to draw on as losses occur later. Weight-bearing exercise at any age slows bone density decline by providing the mechanical loading stimulus that bone requires.