Objective vs self-report assessment of height, weight and body mass index: Relationships with adiposity, aerobic fitness and physical activity

Abstract

Researchers, policymakers and clinicians commonly use height and weight to determine body mass index (BMI) and classify weight status. Self-report measures are widely used but often result in misreported height and weight and, consequentially, underestimation of BMI and-potentially-weight status misclassification. The purpose of this study was to examine differences in objective and self-reported height, weight and BMI values and to find whether discordance is associated with other anthropometric measures, fitness and physical activity. Data were collected from college students through: (a) a pre-consultation online questionnaire where participants self-reported gender, height and weight; (b) an objective fitness assessment that assessed height, weight, body fat percentage, abdominal girth and predicted aerobic fitness; and (c) a post-assessment electronic survey that assessed physical activity. Parametric and non-parametric analyses examined differences between groups. Objective and self-reported height and weight data were collected from 1061 participants, 224 of whom also provided physical activity data. Women significantly under-reported weight (P = .003, η² = 0.02), and both genders over-reported height (P < .001, η² ≥ 0.07), resulting in a significant difference between BMIs calculated using the different measures (P < .001, η² ≥ 0.07) and the weight status misclassification of ~15% of participants. Significant differences were found in anthropometrics, fitness and physical activity based on reporting differences for weight (P ≤ .015) and BMI (P ≤ .015). Students demonstrated a tendency to under-report weight and over-report height, resulting in weight status misclassification. Those who under-reported weight tended to be in poorer health as indicated by lower aerobic fitness and higher abdominal girth and body fat percentage in particular. Further research is required to establish the link between under-reporting weight and over-reporting physical activity.

Keywords: body composition; body mass index; exercise; obesity.