The consequence of encouraging girls to be active for weight loss

Abstract

The purpose of the study, conducted in Pennsylvania, USA, was to assess the prospective effect of parental encouragement of physical activity (PA) for weight loss on adolescent girls' concern about weight, Body Mass Index (BMI) and objectively-measured PA. Non-Hispanic White girls (N = 177) and their parents were assessed when girls were 9, 11, 13 and 15 years old. At each age, girls' concern about their weight, pubertal development, BMI, and dietary intake were measured along with mothers' and fathers' encouragement of PA for weight loss, modeling of PA, and logistic support for PA. At ages 13 and 15 years, girls' PA was assessed using accelerometry. At age 11, girls' PA was measured using a combination of self-report measures and a standardized assessment of cardiovascular fitness. Parents of obese girls reported the highest encouragement of PA for weight loss; however, girls from all weight categories were exposed to encouragement of PA for weight loss and showed similar age-related increases in parental encouragement. Encouragement of PA for weight loss was prospectively associated with higher concern about weight and higher BMI, independent of pre-existing levels of these constructs and covariates. Encouragement of PA for weight loss was not associated with girls' objectively-measured PA. Parental encouragement of PA for weight loss was therefore not an effective strategy in this sample. Findings are consistent with research on parental child feeding practices, where parental control has been linked with unintended negative dietary and psychosocial outcomes among children.

Figure 1

Summary of the analytic model for objective 2 using weight concerns as an example Note; With the exception of baseline weight concerns and breast development (assessed at age 9), all covariates were time-varying and assessed concurrently with encouragement of PA for weight loss. Baseline weight concerns was included in the model as a time invariant covariate to control for pre-existing levels of concern about weight. Similar models predicting BMI and MVPA were run with the exception that the model predicting BMI also included caloric intake as a time-varying covariate and the model for MVPA predicted MVPA at ages 13 and 15 only with baseline PA measured at age 11.

Figure 2

Differential lagged effects of encouragement of PA for weight loss on girls' weight concerns and BMI by age. Note: The unstandardized beta weights (b) reflect the expected differential in the outcome variable for girls exposed to low (score=0) versus high (score = 1) encouragement of PA for weight loss, controlling for covariates. * p <.05 ** p < .01