This work consists of evaluating the effects of a balanced and fortified diet on the nutritional characteristics and values of serum metabolites in protein-deficient rats. A series of three experiments, with 11 lots of 6 rats is conducted, with a control diet containing 20% of protein. The first experiment which lasts 15 days consists of restriction diets containing 10% (P 10), 5% (P 5) and 0% (P 0) of proteins, relative to the control. The second experiment is composed of the same restriction diets (15 days) followed by a rehabilitation diet with the control feed (15 days). The third experiment (30 days) consisted of a restricted period (P0) followed by a single restitution, and a restricted lot (P0F) followed by a restitution fortified with 0.01% of Amin' total in the drinking water. The results obtained indicate that the body weight gain of malnourished rats P10 (1.11 ± 0.34 g), P5 (0.53 ± 0.45 g), P0 (-1.01 ± 0.28 g) is lower than that of the control rats (2.69 ± 0.49 g). The rehabilitation experiment has a minimal impact on body weight gain. On the other hand, fortified rehabilitation rats (P0F) had a body weight gain (3.17 ± 0.85 g) greater than those of rehabilitated rats (P0) (0.57 ± 0.25 g) and control rats (1.36 ± 0.49 g). Malnutrition has variable effects on the average values of blood parameters. In conclusion, protein malnutrition reduces growth in rats. Rehabilitation with a balanced diet alone is not enough to restore nutritional disturbances. To achieve a fast growth, it is necessary to associate with the balanced diet, a fortification with a food supplement enriched with nutrients (essential amino acids, vitamins, trace elements).