THE IMPACT OF PHYSICAL-ACTIVITY ON LIPIDS, LIPOPROTEINS, AND BLOOD-PRESSURE IN PREADOLESCENT GIRLS

Objective. Inconsistent findings reported for the effect of physical a ctivity on lipids, lipoproteins, and blood pressure in children may be due to errors inherent in the methods used to measure physical activi ty, lack of control for other cardiovascular risk factors, or both. Th e purpose of this study was to evaluate the association between physic al activity assessed using direct measures of energy expenditure and c ardiovascular risk factors, controlling for dietary intake and percent body fat. Methods. Nonresting energy expenditure was determined in 49 8- to 11-year-old girls from measurements of daily energy expenditure (using doubly-labeled water, (H2O)-H-2-O-18) and resting metabolic ra te (using indirect calorimetry). Self-reported recall of the hours of participation in physical activities of at least moderate intensity (e nergy expenditure at least four times the resting metabolic rate, METS greater than or equal to 4) during the previous year was also obtaine d. Percent body fat was estimated from the measurement of total body w ater with (H2O)-O-18. Concentrations of total cholesterol, high-densit y lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C) , apolipoprotein B (apo B), apo A-I, lipoprotein (a), insulin, and est radiol, as well as the waist-to-hip ratio, systolic blood pressure, di astolic blood pressure, and dietary intake from 7-day food records wer e measured. Data were analyzed using Pearson product-moment correlatio n and stepwise multiple regression. Results. Self-reported hours of pa rticipation in activities with METS (metabolic equivalents) of 4 or gr eater significantly predicted LDL-C and apo B concentrations, even aft er adjustment for percent body fat and percentage of dietary energy fr om saturated fat. Nonresting energy expenditure adjusted for weight, a measure of the energy spent on physical activity, did not predict LDL -C or high-density lipoprotein cholesterol concentrations. Body mass i ndex and insulin concentration predicted systolic and diastolic blood pressure, respectively. Conclusions. These findings suggest that the i ntensity of physical activity may be a more important determinant of L DL-C in children than the energy spent on physical activity.