Research published on Jan. 23, 2013, in the open access journal Public Library of Science examined the widening gap between obesity levels measured by self reported height and weight and obesity recorded by measured height and weight is increasing.
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 overestimate their own height and underestimate their weight and it is generally assumed that both are responsible for underestimation of self-reported BMI. The authors of this study have shown in previous work that underestimation 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.
Similar comparisons in the United States indicate the same behaviors as presented by the National Health and Nutrition Examination Survey (NHANES) data set.
The authors do not speculate on the rationale behind the obvious self deception in people who are overweight or obese but indicate the inaccuracies in reporting have been used to make erroneous statements of obesity improvement in the United States.
Frances Shiely 1*, Kevin Hayes 2, Ivan J. Perry 1, C. Cecily Kelleher 3
1 Department of Epidemiology and Public Health, University College Cork, Cork City, Ireland, 2 Department of Mathematics and Statistics, University of Limerick, Limerick, County Limerick, Ireland, 3 School of Public Health, Physiotherapy and Population Sciences, University College Dublin, Dublin City, Ireland