Sedentary Behavior Is Independently Related to Fat Mass among Children and Adolescents in South China

Abstract

We aim to explore the independent associations of sedentary behaviors (SB) with body mass distribution among Chinese children. Data on the screen-based sedentary time (television viewing and computer use) and doing homework, physical activities and dietary intake of 1586 Chinese children (50.3% girls) aged 7-15 years were obtained through validated questionnaires. Skin-fold thickness, body height, and weight were measured to calculate percent body fat (%BF), fat mass index (FMI), and fat-free mass index (FFMI). Parental characteristics were collected by questionnaires. Among girls, time of SB (screen time or doing homework) was positively related to %BF, FMI, and FFMI (p < 0.03) after adjusting for maternal overweight, the average annual income of family, moderate-to-vigorous physical activity energy expenditure, and energy intake: Girls in the highest tertile of screen time/homework had 16.7%/23.3% higher relative FMI and 2.9%/2.9% higher relative FFMI than girls in the lowest tertile. Among boys, screen time was positively associated with FFMI (p < 0.003), but not related to %BF and FMI (p > 0.09), while time of doing homework was positively related to %BF and FMI (p = 0.03). Sedentary behaviors might be positively and independently related to fat mass among Chinese children, and were more pronounced in girls.

Keywords: body fat; energy intake; physical activity; sedentary time.

Figure A1

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of time spent on television viewing (h/day) of children stratified by gender (girls ■, boys ). Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)); * p for trend < 0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure A1

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of time spent on television viewing (h/day) of children stratified by gender (girls ■, boys ). Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)); * p for trend < 0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure A2

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of time spent on doing homework (h/day) of children stratified by gender (girls ■, boys ); Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)); * p for trend < 0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure A2

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of time spent on doing homework (h/day) of children stratified by gender (girls ■, boys ); Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)); * p for trend < 0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure 1

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of time spent on screen-based sedentary behaviors (h/day) of children stratified by gender (girls ■, boys ). Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)). * p for trend <0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure 2

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of total time spent on doing homework (h/day) of children stratified by gender (girls ■, boys ). Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)). * p for trend <0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.

Figure 3

Body mass indicators ((a) percentage body fat; (b) fat mass index; (c) fat-free mass index) by tertiles of total time spent on sedentary behaviors (h/day) of children stratified by gender (girls ■, boys ). Data shown are least-squares means (95% CI) adjusted for average annual income of family, maternal overweight, total energy intake (MJ/day) and MVPA energy expenditure (MJ/day)). * p for trend <0.05. p for trend refers to p values obtained by linear regression models with total time spent on sedentary behaviors as continuous variables.