Do Overweight Girls Overreport Physical Activity?

Abstract

Childhood obesity is a growing problem throughout the world,1-3 and one factor believed to contribute to obesity is insufficient physical activity. Studies report that physical activity levels of youth are declining,4 particularly during adolescence.5,6 The relationship between the decline in physical activity and excess weight gain is potentially an iterative loop. Less physical activity may cause weight gain, resulting from a positive energy balance; and weight gain may contribute to real and perceived barriers to being active, resulting in additional weight gain. Some studies examining the relationship between weight status and physical activity levels in adults and adolescents report no significant relationship between physical activity and body fat.7,8 Another report, however, found an association between fat mass and physical activity levels in boys, but not girls.9 A recent study in adults showed that as body fat increases, physical activity objectively measured by accelerometry, decreases.10 One reason for this discrepancy may be the differing choices of physical activity assessment tools. Klesges et al reported that surveys overestimate physical activity compared to accelerometry.11 Furthermore, overweight and obese adults may overreport physical activity levels compared with normal-weight individuals,12 although not all studies have observed this relationship.13 The literature regarding how weight status may influence perceptions of exertion during activity is ambiguous. Epstein et al suggest that overweight children drop out of exercise programs that are perceived to be too strenuous.14 Other studies have noted a direct relationship between rating of perceived exertion (RPE) during exercise and body fat or BMI.15,16 Evidence also suggests that when overweight youth are exposed to a standard exercise bout, they rate exertion levels higher than normal-weight youth do,16,17 particularly at higher levels of intensities of exercise.18 If overweight children perceive a given intensity of physical activity to be more strenuous than normal-weight children do, this perception could contribute to lower likelihood of participation in physical activity and, thus, additional weight gain. To our knowledge, the relationship between weight status and intensity of physical activity, assessed by both objective monitoring and self-report, has not been critically evaluated in adolescent girls. Adolescence is a critical period for girls because their activity levels appear to precipitously decline and because there appears to be a stronger relationship between their activity levels and weight status than there is for boys.19,20 Therefore, the purpose of this study was 2-fold: first, to determine if overweight adolescent girls overreport moderate to vigorous physical activity levels and, second, to determine if overweight girls report, or perceive, specific activities at higher intensity than do normal-weight girls.