The association between mild routine exercise and glucose homeostasis, insulin dynamics, and risk factors for coronary artery disease was investigated in obese adolescent males. Subjects (n = 7; mean +/- SD age 13.3 +/- 1.4 yr) were tested before and after 15 wk of supervised mild intensity exercise. Serum glucose (GLU), insulin (IN), and C-peptide (CP) were measured in response to a mixed meal before and after the 15 wk period. Weight, body composition, peak oxygen uptake (peak VO2), resting blood pressure (BP), and blood lipid levels were also assessed pre- and post-training. After training, percent fat and body weight were not decreased compared to the initial values. Relative changes (p < or = 0.02) in mean values for GLU and peptides after training were: fasting GLU, -15%; total GLU response, -15%; peak IN response, -51%; total IN response, -46%; peak CP response, +55%; and total CP response, +53%. Following training, the subjects did not have an increased peak VO2, but showed consistent reductions in systolic BP and LDL-cholesterol (p < 0.05). Increases in hepatic insulin clearance (decreased insulin levels but increased CP levels) might be training adaptations unique to low intensity exercise or to obese youth. Decreased insulin levels with concurrent decreases in resting blood pressure and the LDL-cholesterol levels suggest that mild exercise training may reduce health risk factors without weight loss in the obese adolescent male.