HORSWILL, C. A., S. H. PARK, and J. N. ROEMMICH. Changes in the protein nutritional status of adolescent wrestlers. Med. Sci. Sports Exerc., Vol. 22, No. 5, pp. 599–604, 1990. The protein nutritional status of adolescent wrestlers was studied to determine whether changes occur during a season of competition and weight loss. Subjects (N = 18) were measured prior to the start of the season (PRE), twice in the midseason, and once during late season (LATE) for weight, percent body fat, and height. At each of these times, a venous blood sample was obtained from the subjects, who were fasted, and analyzed for concentrations of albumin, prealbumin, retinol binding protein (RBP), blood urea nitrogen (BUN), hemoglobin, hematocrit, and 23 amino acids. Diet records were kept by subjects to assess daily energy, protein, fat, and carbohydrate intake. Data were analyzed by repeated measures ANOVA. Results showed that wrestlers decreased weight by an average of 6.6 ± 0.9% and that percent body fat, fat-free weight, plasma levels of prealbumin and RBP, the ratio of total essential amino acids to total amino acids, and dietary energy nutrient intakes were significantly lower at LATE compared to PRE. RBP decreased during midseason and averaged (± SE) 3.21 ± 0.15 mg·100 ml−1 at LATE; prealbumin was significantly lower at LATE with a mean value of 19.8 ± 1.0 mg·100 ml−1. Total energy intake decreased from PRE values by 35%, to approximately 27 kcal·kg−1·d−1 during the season. In conclusion, in these high school wrestlers who lost approximately 6.6% of weight, there were adverse effects on some of the indices of protein nutritional status.