Body composition shifts follow sex-specific paths across adulthood

In a cross-sectional study of 9,717 Caucasian adults aged 20 to 90 years, researchers evaluated sex- and age-specific patterns in body composition using bioelectrical impedance analysis. They measured total body bone, skeletal muscle, fat mass, and intramuscular adipose tissue to identify inflection points and evaluate osteosarcopenic adiposity.

Men showed earlier peaks and midlife stability in bone and muscle, followed by lower values in later life than women. In contrast, women exhibited lower baseline values, multiple early-life inflection points, and sharper midlife downturns around menopause. Fat mass rose steadily in men but followed multiphasic patterns in women, while intramuscular adipose tissue climbed progressively with age in both sexes. Participants meeting criteria for osteosarcopenic adiposity—detected even among the youngest adults—demonstrated earlier downturns in bone and muscle alongside less stable trajectories.