Within- and between-individual variability in estimated energy expenditure and habitual physical activity among young adults.

OBJECTIVE: To examine the within- and between-individual variability in the estimated total energy expenditure (TEE) and habitual physical activity (PA) in free-living young adults. We were specifically interested in the day-to-day variation. DESIGN: Cross-sectional. SETTING: University. SUBJECTS: A total of 277 (125 males, 152 females) participants aged 18-24 years. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Subjects recorded their daily PA with the Bouchard 3-day diary. Descriptive statistics for TEE, moderate-to-vigorous physical activity (MVPA), inactivity (IA), and activity energy expenditure (AEE) were calculated and presented as a frequency distribution. Within- and between-individual variability were tested by RMANOVA and also presented as the coefficient of variation (CV). RESULTS: Mean values for TEE, MVPA, AEE, and IA were comparable between males and females; however, considerable between-individual variability existed. Only MVPA showed a significant difference between sexes (P<0.05), due to slightly greater vigorous PA in males compared to females (8.0 and 6.8 kcal/kg/day, respectively; P=0.12). Results from the RMANOVA revealed no significant day-to-day variability in any TEE or PA variable and the CVs were not significantly different between males and females. TEE and IA displayed mean CVs of approximately 12% while mean CVs for AEE and MVPA approximated 32 and 84%, respectively. CONCLUSIONS: Results from this study suggest (1) a limited day-to-day variability in TEE and (2) a large degree of between-individual variation for TEE and PA exist. This study highlights the importance of understanding the variability associated with TEE, which is important for PA measurement and proper PA and nutritional recommendations. SPONSORSHIP: None.

Utility of pedometer step recommendations for predicting overweight in children.

OBJECTIVE: The purpose of this study was to examine the utility of pedometer-based physical activity recommendations in predicting childhood adiposity. DESIGN: Subjects (n=608) (9.6 years) were from two Midwestern USA communities. Physical activity was assessed by a pedometer. The percentage of subjects meeting physical activity recommendations was determined using published recommendations. Overweight and obesity were determined based on reference values for the body mass index (BMI) developed by the International Obesity Task Force. An elevated waist circumference (WC) was determined based on age- and sex-specific reference values >75th percentile. RESULTS: Children who did not meet the pedometer recommendations were about two times more likely to be overweight/obese and have an elevated WC compared with those meeting recommendations. The BMI and WC were significantly different across pedometer step count groups in males and females. CONCLUSION: Subjects not meeting the recommendations for steps per day were more likely to be classified with the overweight phenotype than those meeting the recommendation. A dose-response relationship between pedometer steps per day and adiposity is also apparent.