Objective To examine the impact of overweight and obesity on quality of life and body image satisfaction in school-aged children, and to assess mediating pathways linking body mass index (BMI) to academic performance. Methods In this cross-sectional study, 380 students in grades 3-5 from a primary school in Jinan, China, were assessed. Anthropometry was used to calculate BMI; physical fitness test performance and academic grades were recorded. Quality of life and body image satisfaction were measured via questionnaires. Differences across BMI categories were compared, and mediation analyses evaluated indirect effects of BMI on academic performance through physical fitness and quality of life. Results The obese group had a higher proportion of boys than girls (68.7% vs 31.3%, P<0.05). Both the overweight and obese groups had lower quality of life than the normal-weight group (P<0.05). Body image satisfaction was negatively correlated with BMI in both males and females (r_s=-0.606, -0.628, respectively; P<0.001). Physical fitness test performance mediated the association between BMI and academic performance (β=-0.098, P<0.001), whereas the mediating effect of quality of life was not significant (P>0.05). Conclusions Overweight and obesity are associated with reduced quality of life in school-aged children, and they are indirectly linked to poorer academic performance through diminished physical fitness.