Your BMI, or body mass index, is used to determine whether or not you have a healthy weight for your size. In previous studies, scientists have demonstrated that you have a tendency to overestimate your own height, whilst underestimating your weight, and this is responsible for under-estimation of self-reported BMI. Frances Shiely and colleagues from University College of Cork, Ireland, who authored this study, have shown in previous work that this underestimation is increasing, and so were led to do this study to determine whether this increasing inaccuracy is due to changing biases in self-reported height, weight, or both.
The team used data from a representative sample of Irish adults, and found that whilst the bias in self-reported height has remained stable over the last ten years, irrespective of gender, age or clinical BMI category, in both genders and all age groups biases in self-reported weight have increased over time. People who are obese most notably have a bias towards reporting that they’re a lower weight than they actually are.
The authors concluded that the benefits of 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.’