Supplementary information
Detailed information on the test battery
Via personal contact and advertisements at the university campus, a clinic for the treatment of eating disorders and a clinic for bariatric surgery 18 young women aged 18 to 28 years covering a BMI range of 13.8 to 61.3 kg/m² were recruited for the photo shooting. They agreed to have their pictures taken when wearing underwear provided by the researchers. All women consented that their pictures would be used in research on body image and for that purpose presented to study participants. The women were paid 70€ for their participation.
All women were then provided with standardized plain skin colored bra and briefs and changed clothes. The photographs were taken by a professional photographer. The full body of the participants was photographed against a uniform blue background in four different positions: front, rear, profile standing and profile sitting. Thus, a picture set consisting of 72 photo stimuli was created (see Figure 1). After the shooting height and weight of each participant were measured (see Table).
Adobe Photoshop (Adobe Systems Inc., San Jose, U.S.A.) was used for image editing. The head of the person was removed to avoid distraction by facial features, expression and hairstyle and the pictures were converted into gray scale to control for effects of skin colour or brightness.
Weight category / Age (years) / Height (cm) / Weight (kg) / Body Mass Index (kg/m²) / Body Mass Index range (kg/m²)Extremely underweight / 19.5 ± 2.1 / 165.7 ± 6.1 / 40.0 ± 0.1 / 14.4 ± 0.8 / 13.5 – 15.0
Underweight / 22.0 ± 0.0 / 167.6 ± 0.8 / 47.0 ± 2.4 / 17.3 ± 0.4 / 17.0 – 18.0
Normal weight / 22.8 ± 2.2 / 170.4 ± 3.6 / 62.8 ± 4.4 / 22.7 ± 2.2 / 20.0 – 22.5
Overweight / 26.5 ± 0.7 / 162.8 ± 6.9 / 72.5 ± 2.1 / 27.4 ± 3.1 / 25.0 – 30.0
Extremely overweight / 25.5 ± 3.5 / 152.8 ± 17.1 / 128.2 ± 30.2 / 56.0 ± 7.6 / 50.0 – 65.0
Table S-1: Characteristics (age, height, weight, BMI) of women’s bodies belonging to different weight categories.
Evaluation study
We conducted an evaluation study to explore whether the stimulus material was suitable for use in adolescent girls, in particular whether the pictures of women belonging to different BMI categories are rated differently in weight and attractiveness by healthy girls.
In the evaluation study we included 37 female adolescents aged 12-18 years attending a local high school. Participants were on average 14.8 ± 1.9 years old with a BMI of 20.9 ± 2.8 kg/m².
Results of the ANOVA with the within-subject factor “BMI category” of the women displayed on the photos (5, “extremely underweight”, “underweight”, “normal weight”, “overweight”, “extremely overweight”) revealed for the weight ratings a significant effect of “BMI category” (F(4,140)=345, p<.001); all participants rated the weight of the different BMI categories significantly different with consistently growing values on the 9-point-scale with growing BMI of the women shown in the pictures (see Figure S-1). The girls also rated the attractiveness of the five BMI categories differently (“BMI category” effect: F(4,140)=161, p<.001). Lowest attractiveness ratings were obtained for extremely overweight, followed by extremely underweight, overweight and normal weight with highest attractiveness ratings for underweight women. These data suggest that the pictures are valid representations of specific weight categories of women’s bodies as rated by healthy adolescents.
Figure S-1: Weight ratings of the healthy adolescent participants of the evaluation study show consistently increasing values on the 9-point scale for increasing BMI of the women displayed in the pictures (mean +/- 2 standard errors).