# Accuracy of Assessing Weight Status in Adults by Structured Observation
## 4 Discussion  
Our findings showed that visual estimation of obesity among adult individuals by trained observers using a body image scale was moderately sensitive (72.8% for overweight/obesity; 41.4% for obesity) and highly specific (78.4% for overweight/obesity; 96.4% for obesity). These results are similar to those reported in studies where healthcare providers estimated patients' weight with an accuracy of 40% to 70% [23; 24; 25; 26; 27; 28; 29; 30]. When combining obesity status with overweight, in order to test the ability of observers to correctly distinguish normal weight from overweight (including obesity), sensitivity increased. It was more likely to correctly classify overweight overall (including obesity) than obesity alone, which may be due to the underestimation of obesity, as reported elsewhere [31; 32; 33; 34; 35]. Underestimation of obesity more than overweight might be explained by normal visual perceptual biases as contraction bias, which means that the weight of obese bodies will be increasingly underestimated as the BMI increases, and by Weber's law, which predicts that change in body size will become progressively harder to detect as their BMI increases [36; 37; 38; 39]. These normal visual perceptual biases are supported by visual normalization theory, in which exposure to larger body sizes changes the range of body sizes that are perceptually judged as being \"normal\" [40; 41; 42; 43]. We should also consider the effect of weight bias caused by negative beliefs about obese individuals and related stereotypes. Data indicate that a wide range of media portray overweight and obese individuals in a stigmatizing manner [44] and, additionally, even health professionals whose careers emphasize research or clinical management of obesity exhibit significant pro-thin and anti-fat bias, indicating a pervasive and powerful stigma [45]. When assigning weight-based descriptors to individuals to assess physician perception of patient weight, women physicians recognized the overweight status of their patients \begin{table}
\begin{tabular}{l c c} \hline \hline  & **Kappa** & **95\%CI** \\ \hline Height (cm) & & \\ \hline \(\leq\)154 & & \\ 155–164 & 0.63 & 0.49–0.76 \\ \(\geq\)165 & & \\ \hline Weight (kg) & & \\ \hline \(\leq\)54 & & \\ 55–74 & 0.46 & 0.31–0.62 \\ \(\geq\)75 & & \\ \hline BMI (kg/m\({}^{2}\)) & & \\ \hline \(<\)18.5 & & \\ 18.5–24.9 & & \\ 25.0–29.9 & & \\ \(\geq\)30 & & \\ \hline \(<\)25 & 0.67 & 0.50–0.83 \\ \(\geq\)25 & & \\ \hline Stunkard Body Figures (1 to 9) & 0.30 & 0.22–0.38 \\ \hline BMI, body mass index. & & \\ \hline \end{tabular}
\end{table} 
Table 4: Concordance between observers regarding estimates of height, weight, BMI, and Stunkard Figures (n = 127 paired observations). more readily than men [46]. In our study, women were also more accurate in visual body weight estimation than men, as female observers estimated obesity with significantly higher sensitivity than male observers. However, the small number of observers does not allow us to draw bold conclusions about this. The gender of the participant has been shown to be associated with differences in the estimation of overweight/obesity. Overweight/obese men were more accurately classified than overweight/obese women. This finding is similar to that reported elsewhere, where physicians of both genders were also less likely to recognize overweight status among female patients [46]. For this study, previous training for observers was performed. Even so, inter-observer reliability results indicate that there is room for improvement in training procedures (namely the inclusion of real people as part of the practical exercises), in order to maximize the concordance between observers, thus reaching more reliable estimations. Testing the concordance between a larger number of observers, as performed in a previous study where the accuracy of visual estimation of weight in geriatric patients by panels of two and three observers was compared [47], would also be an important recommendation for future work.