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 lac king. 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 patt erns of long-term change in midarm muscle area (MAMA) and body fat (waist c ircumference). All patterns of change (loss, maintenance [Delta < 1.3 cm(2) ], or gain of MAMA with concurrent loss, maintenance [Delta < 2 cm(2)] or g ain of body fat), were observed for this sample. After controlling for sex, baseline age, urban residence, height, weight, income, MAMA, waist circumf erence, smoking status, activity level, mean daily energy and protein intak es (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 subj ects who lost arm muscle but gained body fat by lower income and energy int ake at baseline. Although protein intakes at baseline did not differ betwee n the groups that lost arm muscle, protein intakes were significantly highe r for subjects who gained both muscle and fat. Patterns of change involving gains in arm muscle were associated with increased protein intake, urban r esidence, as well as moderate or heavy levels of physical activity at basel ine. Variation in protein intake, physical activity, and urban residence al so differentiated between the groups that gained fat. Patterns of age-relat ed change in body composition appear associated with modifiable variables, including income, urban residence, activity and protein and energy intake.