Body mass index through self-reported data and body image perception in Spanish adults attending dietary consultation

The aim of this study was to explore, based on sex and age, knowledge regarding weight, height, and the perception of body shape in Spanish adults who attend dietary consultation. We also wanted to determine the participants' desired body shapes and what they considered their best health status.

The sample consisted of 8100 women and 1220 men from Spain. They were between the ages of 18 and 75 y. Weight (kg) and height (cm) were measured and body mass index (BMI) was calculated. Participants were nutritionally classified following the cutoffs proposed by the World Health Organization. Each individual was asked about his or her weight and height and self-reported BMI was calculated. They also answered a test of body image perception through drawings of human silhouettes that corresponded to an exact BMI. With this, perceived BMI, desired BMI, and BMI considered healthy were estimated. Parametric statistic tests for contrast of mean and percentages were applied.

Self-reported and perceived BMI underestimate the BMI obtained through anthropometry. Differences between measured and self-reported BMI are lower in women and increase with age in both sexes. The same result was obtained when comparing measured BMI with perceived BMI through silhouette test. On average, desired BMI and healthy BMI were in the limits of normal weight for all ages and both sexes. However, the difference between them was also lower in women.

Age and sex influence the perception of excess weight and body image. This could condition the demand of dietary treatment to improve the nutritional status.