Effects of reducing usual protein intakes in female bodybuilders
Missey, Wendy J.
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The disagreement concerning optimal protein intakes for the strength athlete has caused a lot of conflict between bodybuilders and nutritionists for many years. Now that more women are participating in bodybuilding, the female population should be studied to determine if increased protein is needed to promote positive nitrogen balance. Seven female bodybuilders, ages 23-46, in their maintenance phase of training, volunteered to participate in a 10-day experimental diet, in which their protein intake was decreased from an average of 23.8% to 17.1% of calories representing a percent change of 28.5%, while continuing with their usual caloric intake and exercise regimens. Food and exercise records and twenty-four hour urine collections were collected at four different intervals during the study. One hundred percent remained in the study. After five days on the experimental diet all subjects had negative nitrogen balance and by the tenth day all subjects, except one, remained in negative nitrogen balance but had increased nitrogen balance values. After usual protein intakes were resumed all subjects were in positive nitrogen balance. There was a difference in the effect caloric, protein, carbohydrate and fat intake had on nitrogen balance. Carbohydrate and caloric intake had a moderately strong linear correlation with nitrogen balance and protein had a very strong linear correlation with nitrogen balance, as determined by Pearson's correlation, using a multiple R value, and analysis of variance. Fat demonstrated no significant correlation with nitrogen balance. Exercise consisted of strength training and cardiovascular exercises and was not statistically analyzed in this study. Usual caloric and protein intakes averaged 1700-2100 calories and 94-113 grams of protein. However, many of the subjects deviated from their caloric intakes, resulting in fluctuating protein intakes during the study. These results suggest that caloric and protein intake are both important components in regulating nitrogen balance and that these athletes need increased amounts of protein.