Within-Day Energy Balance, Body Mass Index, and Body Composition in College Students

WITHIN-DAY ENERGY BALANCE, BODY MASS INDEX, AND BODY COMPOSITION IN COLLEGE STUDENTS Rebecca Whitney Leet, Dan Benardot, Walter Thompson, Sarah Henes Background: The customary mechanism for assessing weight change involves an assessment of the imbalance in the energy consumed vs. the energy expended. This energy balance ratio is commonly assessed in 24-hour periods, but this strategy fails to account for the timing of macronutrient intake and within-day fluctuations in energy balance, which have an influence on body composition and, ultimately, weight. Hourly fluctuations in energy balance provides information on the time spent in a catabolic state and time spent in an anabolic state, which is not possible with a 24-hour energy balance assessment. Measuring hourly energy balance to optimize absorption and storage of specific nutrients may be a practical strategy for obese individuals to improve body composition. Purpose: The purpose of this study was to observe current dietary habits and assess hourly energy balance of college students with different BMI categories (i.e., below and above a BMI of 30) to determine if there are differences between body composition and hours spent in different energy balance states. Methods: The subjects completed a four-day diet and physical activity record from which energy intake and energy expenditures from a relative intensity activity scale was predicted linked to MET values. After completing the record, subject weight, height, % body fat and fat free mass was assessed using a multi-frequency bioelectrical impedance segmental body composition analyzer. Results: Data were analyzed from a total of 17 college students (9 men and 8 women) ranging from 20-28 years old (mean age 23 ± 2.6). Predicted energy intake averaged 2237.3 ± 749.3 kcals/d and predicted energy expenditure averaged 2941.7 ± 552.7 kcals/d. The average body fat % of the subjects was 27.1 ± 11.6% and the average BMI of the subjects 28.8 ± 5.8. Using an Independent Samples T-Test, eight subjects with a BMI ≥ 30 spent more time in hours high deficit (< -400 kcals Energy Balance) when compared to nine subjects with a BMI < 30. Nine subjects with a BMI < 30 spent more time in ±400 kcal energy balance. Using a Spearman Rho correlation, body fat % was positively correlated to hours high deficit (p ≤ 0.01) and negatively correlated to hours in ±400 kcal energy balance (p ≤ 0.01). Analysis of men and women found that body fat % of men was not significantly associated to any energy balance variables. While not significant, there was a trend toward a positive correlation between body fat % and hours high deficit (p=0.065) and a negative correlation between body fat % and hours in ±400 kcal energy balance (p=0.065). In women, subjects who spent more time in high energy deficit (< -400 kcals Energy Balance) had higher body fat % (p ≤ 0.05). Subjects who spent more hours in optimum energy balance (± 400 kcal Energy Balance) had lower body fat % (p ≤ 0.05). Conclusions: These data suggest that spending long periods of time in an energy deficit is correlated with higher body fat % and higher BMI in college students. Particularly for women, it may be beneficial for body composition to avoid long periods of time in energy deficit and strive to remain in or near ±400 kcal energy balance. College students may be especially prone to extreme deficits in energy balance because of unpredictable schedules and frequent meal skipping. Recommendations for avoiding large energy deficits throughout the day may be beneficial for this population. Within-Day Energy Balance, Body Mass Index, and Body Composition in College Students A Thesis Submitted to the Graduate Committee in the Division of Nutrition At Georgia State University in Partial Fulfillment of the Requirements for the Degree MASTER OF SCIENCE IN HEALTH PROFESSIONS WITH AN EMPHASIS IN NUTRITION Rebecca Whitney Leet Coordinated Program in Dietetics Department of Nutrition Byrdine F. Lewis School of Nursing and Health Professions Atlanta, Georgia 2014 THESIS COMMITTEE Dan Benardot, PhD, DHC, RD, LD, FACSM (Chair) Walter R. Thompson, PhD, FACSM, FAACVPR Sarah Henes, PhD, RD, LD