A 5-year longitudinal study of changes in body composition in women in the perimenopause and beyond

•Total fat mass and abdominopelvic fat in women declined from the 50–59 age decade.•The decline in appendicular lean mass with age occurred from the 50–59 decade.•There was earlier and greater loss of arm lean mass with implications for exercise strategies to maintain muscle mass. Most studies of the age-related changes in body composition are cross-sectional in design: there have been few longitudinal studies. The aim of this 5-year study was to document body composition changes in perimenopausal and older women. Prospective, longitudinal observational study. 489 women were randomly selected from the electoral roll and stratified into 4 age groups by decade: 40–49, 50–59, 60–69 and 70–79 years. Dual-energy x-ray absorptiometry (DXA) was performed in the first and fifth years of the study. Total body mass (TBM), total fat mass (TFM), total lean mass (TLM), abdominopelvic fat mass, and appendicular fat and lean mass were determined. There were significant increases in TBM (p < 0.001), TFM (p < 0.01), TLM (p < 0.05), arm fat mass (p < 0.05), leg fat mass (p < 0.001) and leg lean mass (p < 0.05) within the 40–49 age decade. TBM, TFM and abdominopelvic fat started to decline from the 50–59 decade. Abdominopelvic fat reduction was significant from the 50–59 decade to the later decades (p = 0.05 to p < 0.001). Arm lean mass showed a significant reduction from the 50–59 decade (p < 0.01). Leg lean mass declined from the 60–69 decade, reaching significance in the 70–79 decade (p = 0.05). TFM and abdominopelvic fat declined from the 50–59 age decade, which is earlier than is suggested in the literature. Conversely, the decline in appendicular lean mass with age occurred later, from the 50–59 decade, with earlier and greater loss in the arms, which has implications for exercise strategies to maintain muscle mass from midlife on.