The purpose of this study was to examine the association of age (young, midlife, and older) and activity level (active and sedentary), determined by a pedometer, with risk factors of chronic disease, including body composition, dietary intake, serum lipids, insulin, leptin, C-reactive protein (CRP), plasma glucose, and resting metabolic rate (RMR) in women across the adult life cycle.
Young (aged 20 to 30 years) (n=49), midlife (aged 40 to 50 years) (n=62), and older (aged 60 years and older) (n=47) women were recruited for this cross-sectional study. For 7 days, participants completed weighed food records and wore a pedometer. Based on the average number of steps per day, the women were further classified as active (>/=7,500 steps per day) or sedentary (<7,500 steps per day). Height, weight, and waist circumference were determined for each participant. Fasting blood samples were taken to assess serum lipid, CRP, insulin, leptin, thyroid stimulating hormone, and plasma glucose levels. RMR and body composition (via dual-energy x-ray absorptiometry) were assessed.
Young and midlife women had lower concentrations compared to older women for serum cholesterol (P<0.01), low-density lipoprotein cholesterol (P<0.01), triglycerides (P<0.01), leptin (P<0.01), and plasma glucose (P<0.01); midlife women had lower serum insulin concentrations vs young and older groups (P=0.01); young women had smaller waist circumference compared to midlife and older groups (P<0.01); percent body fat (P<0.01) and percent fat-free mass (P<0.01) differed between all ages. Lower values were found in active vs sedentary women for serum insulin (P=0.02), serum leptin (P<0.01), waist circumference (P<0.01) and percent body fat (P<0.01). A higher percent fat-free mass (P<0.01) was also found in active compared to sedentary women. No differences were found between activity groups for serum cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, CRP, plasma glucose levels, or RMR. RMR was higher in young and midlife vs the older women (P<0.01). Significant inverse correlations were found between activity (steps per day) and body mass index, insulin level, CRP concentration, leptin level, waist circumference, and body fat. Significant positive correlations were found between age and body mass index, total serum cholesterol level, low-density lipoprotein cholesterol level, serum triglyceride level, leptin level, plasma glucose level, CRP concentration, waist circumference, and body fat. Young and midlife women reported consuming more relative energy (kilocalories per kilogram body weight) and protein (grams per kilogram body weight) than older women (P<0.01). The midlife women reported consuming more dietary cholesterol compared to the young and older women (P<0.01). Active women reported a higher relative energy (kilocalories per kilogram body weight) and protein (grams per kilogram body weight) intake vs the sedentary women (P<0.01). Active women also reported a higher intake of dietary carbohydrates (grams per day, P<0.01; percent of energy, P=0.04).
Overall, these results indicate that younger age and greater physical activity, despite age, are associated with fewer risk factors for chronic disease, such as cardiovascular disease, type 2 diabetes, and obesity.