Physical activity level and body composition in a multiethnic sample of school children in Hawaii

Background: Obesity, particularly in Native Hawaiians, is an important health risk. A possible contributing factor to obesity is reduced physical activity levels. Aim: This study investigates the relationship between measured levels of physical activity and body composition in two grade cohorts of school children of Native Hawaiian/Pacific Islander (NHPI) and non-NHPI ethnicity. Methods: A sample of 105 Kindergarteners and third graders were measured for adiposity, physical fitness, and physical activity levels. Ethnicity was determined from genealogical surveys. BMI, waist circumference (WC) and body fat percentage derived from air displacement plethysmography were used to evaluate adiposity. Maximal oxygen consumption (VO2max/kg) was estimated and total energy expenditure (TEE), physical activity level (PAL) and percentage of time inactive (PTI) were determined using the Flex-heart rate method. Results: VO2max, but not TEE, PAL or PTI, was significantly correlated with BMI in Kindergarteners; while VO2max and PAL were negatively correlated with BMI, PAL was significantly negatively correlated with WC and PTI was positively correlated with fat percentage among third graders. There were no significant ethnic differences in VO2max, TEE, PAL or PTI. Conclusions: PAL and PTI are moderately related to adiposity measures, and there are no ethnic differences in physical activity or fitness measures in this sample.