Some people would explain the extreme skinniness typically seen among high-fashion models in terms of a demand for skinniness on the part of the consumer [of fashion imagery/merchandize]. If this is true, then given that high-fashion models have the highest status among female models, it would appear that the aforementioned demand is especially great and characterizes a substantial proportion of the population, especially young women. This issue needs to be formally addressed.
Let us address a study by Rand and Wright, which evaluated continuity and change in the evaluation of ideal and acceptable body sizes across a wide age span.(1) Salient results from this study are described below, and the paper can be downloaded in pdf format by clicking here.
Rand and Wright evaluated body size preference in a U.S. sample of “303 fourth and fifth-grade elementary school children, 427 high school adolescents, 261 young adult university students, and 326 middle-age adults.” Between three-fourths to four-fifths of the participants in the 4 groups were white. The body size preference was evaluated for 9 series: babies, young boys and girls (ages 6-10), young adult males and females (ages 16-25), middle-aged men and women (ages 35-45) and older men and women (ages 55-65).
The participants were given a series of line drawings -- as in the example of young women shown below -- and asked to circle all figures they considered to be socially acceptable as well as indicate the figure that they found ideal.

Fig 1. Line drawings of young women (ages 16-25).
Most relevant to this site are the figure ratings of the young women (ages 16-25) series by high school and university students. The table below indicates the proportion of each of the four groups that found line drawings 1-9 socially acceptable for the young women series. It is very clear that only a very small minority of people considered body size 1 socially acceptable, and fewer still would consider it ideal. Now, body size 1 is the typical figure of high-fashion models; some high-fashion models would be 1.5 on this scale and very few would be higher still on this scale.

Table 1: Percentage of elementary school children (N = 303), high school adolescents (N = 427), university young adults (N = 261), and middle-age adults (N = 326) rating each body size in Fig 1 socially acceptable.
The table below shows the mean ideal body size in each array, by subject group.

Table 2: Mean ideal body size in each array, by subject group.
The participants overwhelmingly considered the mid-range figures as both socially acceptable and ideal. “Of the 36 mean ratings (9 arrays × 4 groups), 75% (27) indicated a midrange preference for ideal body size (4.0–4.8). The smallest mean ideal body size was 3.3 and the largest was 4.8.”
The results above should be intuitive to most people, a number of whom would be surprised that a study set out to formally demonstrate what in their estimation should be common knowledge. Indeed, anyone who insists that there is a substantial preference for skinny female physiques in the general population, especially among young women, had better cite comparable data and explain away the results above.
Data such as above show that it is absurd to claim that the skinniness of high-fashion models is a response to public demand, especially that of young women, which translates to better sales of fashion merchandize. Whereas top-notch fashion designers will cater to the rich, many of them will also market merchandize to middle class people. Therefore, if public preferences are taken into account to maximize sales, it would make sense to have high-fashion models with a physique in the 3-4 range on the scale shown in Fig 1, but this is not seen. The authors wrote:
Based on the results of this study, we question why the fashion industry and media select as ideal, models who would be considered too thin by most people. The midrange of body sizes within which the ideal is selected by subjects in the present study is rarely used as models. When they do appear, it is not in standard magazines but in catalogues like Lane Bryant, a publication targeted for larger women! (Male fashion models have thinner body sizes than those the subjects selected as ideal, but differences are not as extreme). Even a 30-min exposure to models with normal body sizes can improve how women evaluate themselves (Myers & Biocca, 1992). From a marketing as well as mental health perspective, it would seem advantageous to promote use of midrange rather than very thin body sizes for fashion models.
Guess what? Those who have come to this article without going through the other parts of this site should understand that the typical skinniness of high-fashion models is part of a package of looks -- including youth and masculinization -- that makes them approximate the looks of adolescent boys, and the reason for such looks is that the top-ranks of the fashion business are dominated by male homosexual fashion designers. As to why the looks of fashion models then do not undermine sales, I will repeat an analogy that I have mentioned previously:
Imagine that all companies manufacturing soap use unattractive models to sell soap. Will people stop using soap or even reduce their use of soap as a result? Obviously not. Clearly, if one is selling necessities and highly desirable items, then one has a broad license as to what kind of models one can use. It is important to be well-dressed and even if unattractive women are ubiquitously used to model designer clothing, women are not going to stop desiring such clothing or patronizing fashion designers.
If this study were repeated in non-European cultures, the mean preferred level of body fat in young women would be higher in some cultures, but then women in these cultures are naturally more prone to obesity, and so many of the upper class women in these cultures are overweight/obese that excess body fat becomes a sign of higher social status. It is not necessary to address the relevant genetic differences here, but I will do so if someone raises the issue of body fat preference being largely or entirely conditioned by culture.
References:
- Rand, C. S. W., and Wright, B. A., Continuity and change in the evaluation of ideal and acceptable body sizes across a wide age span., Int J Eat Disord, 28, 90 (2000).