Energy balance

In nonagenarians (≥90 years), declining health (higher frailty index) is associated with an elevation in resting metabolic rate (RMR), which may be driven by decreased muscle mass in women and decreased muscle function (damage) in men.

For those in their 90s, maintaining muscle function is critical not just for movement, but for metabolic health. The study suggests that as health declines, the body burns more energy at rest to maintain itself, potentially draining reserves needed for daily activity. For men, this is linked to muscle damage (enzyme levels); for women, to muscle mass. Preserving muscle quality and quantity may help manage this increased metabolic burden.