Within-Day Energy Balance and Protein Intake Affect Body Composition in Physically Active Young Adult Females

Title: Within-Day Energy Balance and Protein Intake Affect Body Composition in Physically Active Young Adult Females Background: Past studies suggest that individuals who eat smaller, more frequent meals are at a metabolic advantage when compared to those who eat larger, less frequent isocaloric meals. Studies also suggest that consumption of small amounts (~ 20 to 30 g) of protein evenly distributed during the day, may be a superior strategy for satisfying the protein requirement and improving muscle protein synthesis. It was, therefore, the purpose of this study was to assess the relationship between body composition and the distributed consumption of energy and protein in physically active young adult females. Methods: Using an IRB approved protocol, physically active female volunteers were measured for height using a standard wall mount stadiometer; body composition and weight were measured using a multi-current 8-mode segmental bioelectrical impedance device (Tanita, Arlington Heights, Illinois USA, Model BC-418). The volunteers kept a food and activity journal for one day, which was assessed to determine hourly energy balance and hourly protein intake. Exertion was assessed using a relative intensity activity MET value scale that produces multiples of resting energy expenditure, which was predicted using the Harris-Benedict equation. Results: The 28 females who volunteered for this study ranged in age from 19-24 years. Significant inverse associations were found between protein (grams/kg) consumption and fat mass (r=-0.42; p=0.026); and FFM and the ratio of protein to energy balance at 4pm (r=-0.376; p=0.049). There was a significant positive association between FFM and the ratio of protein to energy balance at 12pm (r=0.390; p=0.040) and 9pm (r= 0.379; p=0.047). There was also a significant positive association between the ratio of FFM to height and the ratio of protein to energy balance at 12 pm (r=0.423; p=0.025). There was a significant association between highest daily peak energy balance and FFM to height ratio (r=0.402; p=0.034). Regression analysis determined that independent EB and protein variables could be used to predict the dependent variable FFM to Height ratio (r=.727; p=0.019). Conclusions: These findings demonstrate a significant positive association between highest daily EB and FFM to height ratio. The results also suggest that higher protein consumption per kg is inversely associated with fat mass. Similarly, when protein is consumed when in ±400 kcal energy balance, is associated with higher FFM. Additionally, energy balance and protein variables can be used to predict FFM to height ratio using a regression equation that accounts for 52.9% of variance. These data indicate that subjects spent far more hours in an energy balance deficit than surplus, making it difficult to assess the impact of protein intake distribution on body composition. It does appear that, from a relatively small subsample (n=28) who did achieve a positive withinday energy balance and adequate protein intake, consumption of protein while in good energy balance may help physically active adult females achieve a body composition that is low in fat mass and high in lean muscle mass. Within-Day Energy Balance and Protein Intake Affect Body Composition in Physically Active Young Adult Females by Heather L. Hanson A Thesis Presented in Partial Fulfillment of Requirements for the Degree Master of Science in Health Sciences The Byrdine F. Lewis School of Nursing and Health Professions Department of Nutrition Georgia State University Master’s Thesis Advisory Committee: Dan Benardot, PhD, RD, LD, FACSM (Chair) Anita M. Nucci, PhD, RD, LD Walter R. Thompson, PhD, FACSM, FAACVPR