Objective: Childhood obesity is an ongoing public health problem. Researchers have identified dietary energy density (ED, kcal/g), an established marker for diet quality, and sedentary behavior as risk factors for obesity during childhood, but little is known about the relationship between diet and factors associated with fitness during early childhood and adolescence. The objective of the present study was to evaluate the relationship between diet quality and various markers of physical fitness, including locomotor development and enjoyment of physical activity in nationally representative sample of US children.

Methods: A secondary data analysis of 1,518 children age 3-15 years old who participated in the 2012 National Health and Nutrition Examination Survey National Youth Fitness Survey (NYFS) was completed for this study. The dataset contains information about dietary intake, locomotor development, and physical activity for all participants. Dietary intake information was collected using 24-hour recall, and assessment of diet quality involved calculation of dietary energy density. Multivariable linear regression was used to compare stratum-specific mean estimates of dietary energy density for children adjusting for age, sex, race, household income, and body mass index percentile.

Results: In the present study, we observed a negative linear relationship between dietary energy density and locomotor skills (p-trend=0.01); children with the lowest locomotor skill scores had higher dietary ED than children with the highest locomotor skill scores (1.85±0.03kcal/g vs. 1.56±0.07kcal/g p=0.002). In older children, a negative linear trend between dietary ED and self-reported enjoyment of participation in physical education or recess (p

Conclusions: The results indicate that dietary ED in early childhood is inversely associated with locomotor skill score, and diet in older children corresponds with enjoyment of physical activity in older children. Consuming a diet low in ED may therefore represent dietary behaviors that support physical activity in children.