Wearable Camera-Based Objective Screen Time and Its Combined Associations with Dietary and Physical Activity Factors in Relation to Childhood Obesity

<b>Background and objectives</b>: The objective of this study was to test the effects of objectively measured screen time using wearable cameras, along with dietary intake and physical activity level (and their interaction), on obesity among Chinese school-aged children. <b>Methods</b>: This study was conducted among 52 fourth-grade children (age: 9.76 ± 0.44; 50% boy) in Beijing, including children with obesity and age- and sex-matched normal-weight controls. Screen time (min/day) was coded from wearable camera images collected over one week using image recognition, physical activity measured using accelerometers, and dietary intake via camera-assisted 3-day 24 h dietary recalls. Logistic regression and generalized additive models assessed associations with obesity indicators, including general (obesity; percentage of body fat, BF%) and central (waist circumference; weight-to-height ratio). The combined effects of screen time with dietary and physical activity factors were also analyzed. <b>Results</b>: Children with obesity had longer daily screen time (94.91 ± 35.44 vs. 83.15 ± 36.86 min). Longer screen time was associated with higher energy and carbohydrate intake, more average duration per meal, a higher proportion of meals with screen, increased sedentary time, and a lower proportion of time spent in moderate-to-vigorous physical activity (MVPA). After adjusting for dietary intake and demographic covariates, longer screen time (≥1.3 h/day) was linked to higher odds of obesity (OR = 4.25, 95% CI = 1.09, 16.53) and BF% (OR = 6.14, 95% CI = 1.29, 29.10). Less protein intake (OR = 9.57, 95% CI = 1.31, 70.14), more proportion of meals with screen (OR = 6.40, 95% CI: 1.22, 33.61), less proportion of meals with social interaction (OR = 5.90, 95% CI: 1.01, 34.59), and less MVPA (OR = 5.21, 95% CI = 1.11, 24.43) with more screen time increased obesity risk. <b>Conclusions</b>: Objectively measured screen time was positively associated with the risk of childhood obesity. Longer screen time combined with lower protein intake, a higher proportion of meals consumed while watching screens, less meals with social interaction, and lower MVPA may collectively increase obesity risk. These findings call for efforts to reduce screen exposure, promote MVPA, and increase dietary protein intake. Additionally, encouraging children to avoid screen use during meals and promoting parent or peer companionship during eating may help reduce the risk of childhood obesity.