(1) Background: Sedentary behavior is increasing in all age groups and is one of the most common lifestyles that is a risk factor for overweight and obesity; however, few studies have evaluated the impact of leisure-time sedentary behavior on overweight and obesity. This study aims to examine the distribution characteristics of different leisure-time sedentary behaviors and their effects on excessive weight in different age groups in the Chinese population to provide evidence for the development of behavioral interventions. (2) Methods: This study utilizes data from the 2004 to 2011 China Health and Nutrition Survey (CHNS). Participants ranged in age from 6 to 18 years or older and were from China. Weight and height were measured in the physical examination, and the sedentary behavior times during leisure periods were collected by using a questionnaire. Logistic regression models were performed for association analyses. (3) Results: A total of 36,169 participants were included in this study. The impact of screen-based sedentary leisure time on excessive weight is greater in middle-aged and older adults. For middle-aged adults, sedentary time periods spent on the Internet or video games were found to be significantly and positively associated with excessive weight (OR, 1.122, 95% CI, 1.005–1.253). In addition, for older adults, sedentary time periods spent watching television or videos were found to be significantly and positively associated with excessive weight (OR, 1.065, 95% CI, 1.035–1.095). (4) Conclusions: This study helps grasp the target population and provide evidence for the development of behavioral intervention guidelines.

Background: This study aimed to investigate the changes in distinct types of screen time and explore their longitudinal association with children and adolescents’ weight status. Methods: A two-wave longitudinal study was conducted among 2228 children and adolescents (6–19 years) in Shanghai, China, before and during the pandemic. Recreational screen time (watching TV/videos, online gaming, using social media, and browsing webpages), educational screen time (online homework and online class), and BMI were measured using a self-reported questionnaire. Mixed-effects models were constructed to assess the associations between screen time and weight status. Results: The prevalence of overweight and obesity was 20.5% and 10.2% at baseline, respectively. Both recreational and educational screen time increased significantly over two months. While recreational screen time was found to be a risk factor for obesity, it was not the case for educational screen use. Specifically, adolescents who spent more time watching TV/videos had a higher obesity risk (OR = 1.576). No significant associations were found in children. Conclusions: Overweight and obesity were prevalent among children and adolescents in China. Reducing screen-based activities is a promising strategy to prevent unhealthy weight gain in Chinese children and adolescents, while it is necessary to consider the content and distinguish between educational and recreational screen use.