Serum iron (sFe), and ferritin (sFert), transferrin saturation index (TSI), plasma zinc and copper (pZn, pCu), and erythrocyte zinc content (eZn) were measured in 55 obese children and adolescents (28 males and 27 females) before and after a 13-wk treatment with a hypocaloric balanced diet (HCBD, 22 subjects) or a 10-wk treatment with a protein sparing modified fast diet (PSMF, 33 subjects). The energy intake provided by the HCBD and PSMF diet was calculated to be 60 and 25%, respectively, of the recommended dietary allowances (RDAs) for age and sex. Neither diet was supplemented with trace elements or calcium. Using a visual memory system, all subjects had a 24-h dietary intake recall before starting the weight-loss program. Iron, zinc, and copper intakes from the 24-h recall were compared with those from prescribed diets. Both diets produced a significant (p < 0.001) weight reduction with a significant reduction in the arm muscle area of the PSMF group. After treatment, no significant change was observed in sFe, sFert, and TSI of either group, whereas eZn increased significantly in the HCBD and the PSMF groups (p = 0.001 and p < 0.006, respectively), with an improvement of the erythrocyte index (E.I.). A significant increase in pZn was also observed in the PSMF group (p = 0.007).