Relative influence of diet and physical activity on body composition in urban Chinese adults

The relative influence of diet and physical activity on body fatness remains uncertain. The objective of the study was to investigate associations of dietary variables and physical activity with body fatness in urban Chinese adults. We conducted a cross-sectional study in 130 weight-stable men and women aged 35-49 y. Subjects were selected from upper and lower tertiles of dietary fat and physical activity on the basis of screening questionnaires. Dietary intake was assessed by weighed food intake, physical activity level (PAL) was calculated as the ratio of predicted total energy expenditure (TEE) to predicted resting energy expenditure, and body composition was measured with the use of (2)H(2)O. Reported energy intake and predicted TEE were validated against TEE determined with the use of (2)H(2)(18)O (n = 73). Body fatness was positively associated with dietary variety (ie, variety of ingredients) (partial r = 0.186, P = 0.039) and frequency of consuming restaurant foods (partial r = 0.237, P = 0.001) and negatively associated with PAL (partial r = -0.307, P = 0.001) in a multiple regression analysis that controlled for sex and confounders. The combined variance accounted for by dietary variety and restaurant food consumption (9.1%) was equivalent to that for PAL (9.4%). Neither dietary fat nor energy density predicted body fatness, but dietary energy density predicted within-subject day-to-day variation in reported energy intake (P < 0.001). Dietary variety, frequency of restaurant food consumption, and PAL significantly predicted body fatness in urban Chinese adults, but dietary fat did not. These findings support previous studies in US adults and suggest that dietary variables other than fat have an important influence on adult body composition.