Relations of parental obesity status to physical activity and fitness of prepubertal girls.

OBJECTIVE To determine whether physical activity and fitness differ among normal-weight-for-height, multiethnic, prepubertal girls whose parents are lean, obese, or both. SETTING Conducted in Houston, Texas. STUDY PARTICIPANTS Normal-weight white, black, and Hispanic prepubertal girls (mean age +/- standard deviation: 8.5 +/-.4 years) participated in this study. Girls were recruited according to parental leanness or obesity defined as follows: girls with 2 lean parents (LN group; n = 30); girls with 2 obese parents (OB group; n = 27); and girls with 1 lean and 1 obese parent (LNOB group; n = 44). Intervention. Each child wore a heart rate monitor for two 24-hour periods, underwent a treadmill exercise test, answered an activity questionnaire, and completed energy expenditure measurements by basal calorimetry and doubly labeled water. OUTCOME MEASURES The amount of time spent above 125% and 150% of basal heart rate (BHR) was calculated during each 24-hour period (n = 84). Fitness (n = 97), habitual physical activity (n = 101), and physical activity level (PAL = total energy expenditure/basal metabolic rate; n = 101) were also measured. RESULTS The times spent above 125% and 150% of BHR were similar among LN, LNOB, and OB groups. Black girls spent less time than did white girls on the weekend above 125% BHR and above 150% BHR. No significant familial or ethnic differences in peak oxygen consumption or habitual physical activity were observed. PALs were as follows: LN = 1.6 +/-.21; LNOB = 1.64 +/-.27; OB = 1.58 +/-. 20; white = 1.63 +/-.23; black = 1.58 +/-.24; and Hispanic = 1.65 +/-.25. PAL was related to time spent above 125% BHR and 150% BHR (r =.31,.39). CONCLUSIONS Physical activity and fitness of normal-weight prepubertal girls predisposed to obesity did not differ from girls without a family history of obesity. obesity, children, energy metabolism, exercise, heart rate monitoring.