Patterns of long-term change in body composition are associated with diet, activity, income and urban residence among older adults in China.

Studies describing patterns of long-term change in body composition are lacking. Using longitudinal data on 608 healthy, nonobese Chinese (aged 50-70 y) from the 1993 and 1997 China Health and Nutrition Surveys, this article describes the prevalence, sociodemographic and lifestyle correlates of patterns of long-term change in midarm muscle area (MAMA) and body fat (waist circumference). All patterns of change (loss, maintenance [Delta < 1.3 cm(2)], or gain of MAMA with concurrent loss, maintenance [Delta < 2 cm(2)] or gain of body fat), were observed for this sample. After controlling for sex, baseline age, urban residence, height, weight, income, MAMA, waist circumference, smoking status, activity level, mean daily energy and protein intakes (from three 24-h recalls), and change in height, it was determined that subjects who lost both arm muscle and body fat were distinguished from subjects who lost arm muscle but gained body fat by lower income and energy intake at baseline. Although protein intakes at baseline did not differ between the groups that lost arm muscle, protein intakes were significantly higher for subjects who gained both muscle and fat. Patterns of change involving gains in arm muscle were associated with increased protein intake, urban residence, as well as moderate or heavy levels of physical activity at baseline. Variation in protein intake, physical activity, and urban residence also differentiated between the groups that gained fat. Patterns of age-related change in body composition appear associated with modifiable variables, including income, urban residence, activity and protein and energy intake.