[Effects of rapid weight reduction diet on protein metabolism and physical performance]

The purpose of this study was to provide information on the requirement of nutrition, especially of the protein during rapid weight reduction immediately before a competition of a weight-classification system sport, boxing. Weight reduction period was 9 days. Subjects were divided into three groups of free diet group (group A: n = 5), high protein diet group (group B: n = 5) and ordinary protein diet group (group C: n = 4). Group A had taken food ad libitum. Group B had taken 2.0 g/kg/day of protein in the first half and 1.5 g/kg/day of protein in the second half of weight reduction period, and Group C had taken 1.0 g/kg/day of protein throughout weight reduction period. Groups B and C had taken 2,000 kcal/day in the first half and 1,200 kcal/day in the second half of weight reduction period. Anthropometry and nutritional investigation were performed, and urine components were analyzed. The main results obtained were as follows: 1) Calorie and protein intake in Group A averaged 883 kcal/day and 0.9 g/kg/day in the second half of weight reduction period. 2) 3-methylhistidine and urea nitrogen in urine and 3-Me/Cr increased significantly at the end of weight reduction period in Group A, but decreased significantly in groups B and C. Nitrogen balance changed to a negative value only in group A. Differences in each of urine components were statistically significant between group A and the other two groups at the end of period. 3) Heart rate and oxygen intake at the same submaximal work load increased significantly in group A at the end of weight reduction period, but in groups B and C no noticeable changes were observed.(ABSTRACT TRUNCATED AT 250 WORDS)