Visceral fat is highly correlated with metabolic syndrome in obese adolescents. The aims of this study were to determine the prevalence of metabolic syndrome and to assess the effect of a long-term (1 year) intervention with multidisciplinary therapy in predicting metabolic syndrome among obese adolescents, as well as to compare short- with long-term therapy. Eighty-three postpuberty obese adolescents were recruited, including 37 boys (body mass index [BMI], 36.19 +/- 3.85 kg/m(2)) and 46 girls (BMI, 35.73 +/- 4.42 kg/m(2)). Body composition was measured by plethysmography using the BOD POD body composition system (version 1.69, Life Measurement Instruments, Concord, CA), and visceral fat was analyzed by ultrasound. Metabolic syndrome was determined according to the World Health Organization criteria. Patients were assigned to a weight loss multidisciplinary intervention consisting of nutritional, exercise, psychological, and clinical therapy. At the beginning of therapy, we found that 27.16% of the obese adolescents presented metabolic syndrome, whereas only 8.3% did so after intervention. Indeed, in boys, BMI (36.19 +/- 3.85 to 32.06 +/- 5.85 kg/m(2)), visceral fat (4.88 +/- 1.35 to 3.63 +/- 1.71 cm), homeostasis model assessment of insulin resistance (4.77 +/- 3.41 to 3.18 +/- 2.33), and percentage of body fat (38.24% +/- 6.54% to 30.02% +/- 13.43%) presented a statistically significant reduction; and their fat-free mass percentage increased (62.14% +/- 5.78% to 69.17% +/- 12.37%). In girls, after long-term therapy, BMI (35.73 +/- 4.42 to 33.62 +/- 3.78 kg/m(2)), visceral fat (3.70 +/- 1.40 to 2.75 +/- 1.01 cm), and percentage of body fat (46.10% +/- 5.66% to 39.91% +/- 5.59%) showed a statistically significant reduction; and their fat-free mass increased (53.61% +/- 5.65% to 59.82% +/- 5.78%). In conclusion, long-term multidisciplinary therapy was effective in promoting beneficial changes in some predictors and decreasing the prevalence of metabolic syndrome in obese adolescents.