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Self-Reported BMI Bias Estimates Increasing Due To Weight Bias, Not Weight Loss

Widening gap in estimates of partially due to biased self-reports

The gap between measured by self-reported and obesity recorded by measured is increasing.  This is due to an increasing bias in self-reported weight, according to research published January 23 in the open access journal PLOS ONE by and colleagues from University College of Cork, Ireland.  

BMI is a ratio of height and weight used clinically to assess whether an individual’s weight is in a healthy range. Previous studies have shown that people tend to over-estimate their own height and under-estimate their weight and it is generally assumed that both are responsible for under-estimation of self-reported BMI. The authors of this study have shown in previous work that under-estimation of BMI is increasing over time. Here, they assess whether this increasing inaccuracy is due to changing biases in self-reported height, weight, or both, using data from a representative sample of Irish adults.  

The researchers found that the bias in self-reported height has remained stable over the last ten years regardless of gender, age or clinical BMI category. However, biases in self-reported weight have increased over time for both genders and in all age groups. The bias towards reporting a lower weight is most notable in those who are obese. The authors state that knowing why self-reported BMI scores are decreasing while clinically measured BMIs are not “brings us one step closer to accurately estimating true obesity levels in the population.”


“Height and : The Influence of Time”, Shiely F, Hayes K, Perry IJ, Kelleher CC.
PLOS ONE 8(1): e54386. doi:10.1371/journal.pone.0054386

Financial Disclosure: This work was not funded but was conducted under the auspices of the HRB Centre for Diet and Health Research. The HRB had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interest Statement: The authors have declared that no competing interests exist.