Doctoral Dissertations

Date of Award

5-1991

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Education

Major Professor

Edward T. Howley

Committee Members

Jean Lewis, Wendell Liemohn, Mary Sue Younger, Bill Wallace

Abstract

The body weight and composition manifested by an individual at any point in time represents the cumulative effect of the energy intake and expenditure by that individual. The amount of weight lost or gained by an individual is related to his or her ability to maintain a state of negative or positive energy balance. Excessive weight gain will most likely be exhibited by excessive quantities of subcutaneous adipose tissue. Maintaining high levels of body fat can be detrimental to an individual's health. In recent years there has been a heightened interest in the interaction of exercise, nutrition and health. Simultaneous to the increased sensitivity to the role nutrition plays in health has been an increased appreciation for the the role it may play in physical performance. The number of females participating in physical activity for health and competitive reasons has also risen in the last twenty years. In spite of the increased participation by females, the majority of exercise and nutrition studies have used male subjects. Due to the physiological differences between males and females it is no longer acceptable or prudent, to extrapolate the data from males to females.The energy intake and expenditure by active females will determine the state of energy balance. Maintaining a positive or negative energy balance for an extended period of time will have significant consequences for performance. Exercise has been known to produce a hypophagic effect in some males and females. Circulating catecholamines have been proposed as a potential mechanism to explain this response. It has been suggested that female athletes chronically maintain an energy expenditure greater than their energy intake, without significant losses of body weight. Significant changes in resting metabolic rate and/or energy intake may explain the ability of some female athletes to maintain weight in spite of the energy deficits created by the high caloric demands of training. Hunger, appetite (food intake), and urinary catecholamine (epinephrine, E and norepinephrine, NE) responses to an acute bout of exercise and control session were studied in trained female runners (R) and swimmers (8). Resting metabolic rate (RMR) of the trained (T) subjects was compared to untrained (LIT) sedentary controls (0). Mode did not influence the hunger or catecholamine response of the trained females. Hunger increased with time after the exercise session. Correlation coefficients indicated there was a significant relationship between the post exercise hunger ratings and circulating levels of NE. In addition NE was a significant predictor of appetite (food intake) following exercise, but not the control session. Hunger was not related to food intake following control or exercise session. There were no differences in food intake across sessions or groups. Resting metabolic rate expressed as kcal/ kg LBW was lower in trained (T) females as compared to untrained (UT) controls. Hunger and appetite responses appear to be dissociated in female runners and swimmers. Appetite appears to be a function of a multitude of physiological, psychological and environmental stimuli. The role any one stimulus plays in the appetite response of the female is not clearly defined at this time. Female runners and swimmers resting metabolic rate may reflect an adaptation to chronic levels of low energy intake against high energy expenditures.

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