IntroductionOverweight and obesity are a growing global public health threat increasingly prevalent among adolescents in low-income and middle-income countries such as Nepal. These conditions are influenced by multifaceted social, behavioural, and habitual factors. Adolescents are particularly at risk due to changing dietary and lifestyle patterns. Additionally, the current nutritional shift, economic progress and rapid urbanisation pose significant threats to nutrition-related health outcomes. This study aims to assess the prevalence and factors associated with overweight and obesity among adolescents in Nepal.MethodsA school-based cross-sectional study was conducted from September 2022 to January 2023 among 768 randomly selected adolescents from 10 schools in the Nagarjun municipality of Nepal. Anthropometric measurements of height and weight were assessed using standard tools, and the corresponding body mass index (BMI) was calculated. Factors associated with overweight/obesity were examined using the χ2tests, followed by logistic regression analyses. The statistical significance was set at p<0.05 and 95% Confidence Intervals (CIs).ResultsThe overall prevalence of overweight/obesity among adolescents was 6.38% (95% CI 4.64% to 8.11%). The mean weight, height and BMI of the participants were 50.22±9.37 kg, 160.17±9.14 cm and 19.56±3.24 kg/m2, respectively. Adolescents studying in higher grades (AOR 3.61, 95% CI 1.26 to 10.30), uninvolved in any kind of physical activity (AOR 4.97, 95% CI 2.38 to 10.34) and various games and extracurricular activities at school (AOR 2.49, 95% CI 1.16 to 5.28) and consuming high-calorie sugar-rich foods as lunch (AOR 3.02, 95% CI 1.31 to 6.94) were more likely of being overweight/obese than their respective counterparts.ConclusionOverweight and obesity are significantly influenced by lifestyles that involve minimal to no physical activity and by the dietary habits of adolescents. The findings warrant interventions in educational and home settings aiming to improve the lifestyles of adolescents.