The present study was designed to examine the effect of protein malnutrition and nutritional recuperation on metabolic and hormonal adaptations in young trained rats. In two separate experiments, six groups of young male rats were differently fed. During the first month, a normal-protein diet (NP) and a low-protein diet (LP) groups received 17% and 6% of casein, respectively. Following this period half of rats were sacrificed and other half were assigned to four groups: sedentary (SG); trained (TG), sedentary recuperate (SRG) and trained recuperate (TRG). During this second month all rats received a normal-protein diet. TG and TRG performed a swimming exercise protocol (overload of 5% body weight). LP rats presented reduced serum total protein levels (7.21±0.32 g/dL; n=11); glucose (116±11 mg/dL; n=11) and insulin (1.39±0.35 ng/mL n=11) when compared to NP(7.61±0.22 g/dL, n=10; 129±11 mg/dL n=10; 2.60±1.11 ng/mL, n=10, respectively; p<0.05). SRG and TRG rats showed no significant decrease in the serum total protein levels but the SG and TRG presented a higher concentration of serum glucose (142±10 mg/dL, n=6; 140±7 mg/dL, n=5, respectively) when compared to TG (130±8 mg/dL, n=7, p<0.05). The SRG showed a higher concentration of serum insulin when compared to SG (3.28±0.55 ng/mL, n=6; 2.38±0.71 ng/mL, n=8, respectively; p<0.05). In conclusion, the effect of low-protein diet followed by nutritional recuperation led to augmented levels of glucose and insulin but exercise did not affect this response. When a low-protein diet was not present, exercise decreased the level of glucose.