In order to evaluate the influence of physical exercise and protein intake on Resting Metabolic Rate (RMR) and Postprandial Energy Expenditure (PEE), 16 healthy, normal-weight, 15 year-old, adolescent males at the same stage of pubertal development were studied. They were assigned to two dietary groups receiving the same energy intake (1.3 x by measured RMR) and different proportions of macronutrients (13% protein, 39% fat, 48% CHO in Group A; 30% protein, 32% fat, 38% CHO in Group B). An increase in postprandial energy expenditure, relative to basal, was observed in all individuals. The postprandial energy expenditure was higher in group B than in group A. Postprandial Post-exercise Thermogenesis (expressed as Kcal/3 h) was significantly higher in group B than group A (p < 0.05). Although the RMR on the test day was not different between the groups, the RMR on day 2 was significantly higher than on day 1 in group B (p < 0.01). In group B, the post-exercise RQ was significantly lower than the preexercise RQ (p < 0.01). It is concluded that in normal-weight-adolescents, a hyperproteic diet followed by moderately-intensive exercise induces increases in EE and decreases in RQ in the postprandial post-exercise period and is accompanied by increase in the RMR the following day.