Background The prevalence of overweight and obesity in Chinese children and adolescents was increasing during the past few decades. The goal of this study was to investigate the effects of after-school exercise with or without diet restriction on total and central obesity, fitness level, and metabolic profile in overweight Chinese adolescents.Methods A ten-week weight loss trial was performed using a 2×2 block design (exercisexdiet). Ninety-three overweight adolescents (average age:(13.6±0.7) years; body mass index (BMI): 22.4-34.1 kg/m2) were randomly assigned to four groups:1) diet (D); 2) exercise (EX); 3) diet plus exercise (DEX); and 4) overweight control (C). Caloric intake recipes were enacted based on individual age and corresponding ideal body weight. One-hour after-school exercise was performed once per day, four days per week for ten weeks. Changes of anthropometry, body composition, aerobic fitness,and metabolic biomarkers were determined.Results Groups D, EX and DEX had a significant decrease in BMI (P＜0.01) after the intervention. The percentage of body and truncal fat, and waist circumference were independently reduced by exercise (P＜0.05 and P ＜0.01), but not diet. The decrease in body fat percentage was positively related with the exercise compliance (r=0.34,P=0.01). Exercise decreased truncal fat percentage and waist circumference, suggesting a reduction of central adiposity, but did not significantly affect body weight and BMI. Exercise significantly reduced serum low-density lipoprotein cholesterol (P=0.037), which was positively correlated with decreases of truncal fat percentage (r=0.222, P=0.048). No significant effects of interventions on insulin sensitivity, early insulin release index, and aerobic fitness were observed.Conclusion At least twice a week of one-hour after-school exercise significantly attenuated central adiposity and had a significant impact on lipid profiles in overweight Chinese adolescents.