Body composition changes in stable-weight elderly subjects: the effect of sex.

BACKGROUND AND AIMS: Although cross-sectional and longitudinal studies have shown age-related changes in body composition and fat distribution, they may be related to body weight changes. The aim of this study was to evaluate yearly age-related changes in body composition and fat distribution, over a two-year period, in 101 women and 60 men (age range: 68 to 78 years at baseline).

METHODS: Body composition was evaluated by dual energy X-ray absorptiometry (DXA), and fat distribution by waist and hip circumferences and waist-to-hip circumference ratio. Baseline free testosterone, IGF-1 and serum albumin were evaluated in all subjects, as well as physical activity. Clinical evaluation was performed at baseline and yearly in order to exclude subjects with any condition inducing pathological changes in body composition or fat distribution. Subjects with a weight change > 5% of their baseline body weight during the study period, were excluded.

RESULTS: Significant increases occurred in Body Mass Index (BMI) (1.18% in women, 1.13% in men), waist (1.75% in women, 1.39% in men), and hip circumference (1.06% in women, 1.31% in men), whereas height decreased significantly in both men (0.42%) and women (0.55%). Significant increases in total body fat (1.31%) and percent body fat (1.27%) were observed in women but not in men. Lean body mass did not change significantly throughout the study in either sex. Significant losses in leg muscle mass and appendicular skeletal muscle mass (ASM), calculated as the sum of arm and leg fat-free soft tissue, were observed in men (respectively 3.56 and 2.77%) and women (respectively 2.41 and 1.59%). A significant decrease in ASM adjusted by stature (ASM/height2), a proposed proxy for sarcopenia, was found in men only (1.97%). The rates of loss in leg muscle mass and appendicular muscle mass were significantly higher in men than in women, even after adjusting for free testosterone, IGF-1, physical activity and serum albumin.

CONCLUSIONS: These data demonstrate significant changes in body composition and fat distribution in independently living, weight-stable elderly men and women. These changes are dependent on sex and independent of physical activity, hormones or serum albumin.