Background
The growing rate of obesity in children and adults is a global health concern. In European countries, about 20% of children and adolescents and 30 to 80% of adults are overweight or obese with rising secular trends. High levels of overweight affect both Eastern and Western European countries [
1,
2]. Corresponding to this trend, large proportions of the population are unsatisfied with their weight and trying to lose weight. In addition to actual weight,
perceived weight status is an important determinant of eating and weight-loss behaviour [
3‐
7].
Perceived weight does not always reflect actual weight status based on body mass index (BMI). Studies have shown that despite low rates of obesity, many university students, especially women, perceive themselves as overweight [
5,
8‐
11]. This is of concern, because inappropriate weight perceptions can lead to unhealthy behaviours including eating disorders [
5,
12,
13]. Universities and colleges, on the other hand, represent an opportunity for reaching a large number of students to promote appropriate weight perceptions and healthy eating behaviours [
13].
Actual weight and weight perceptions may be influenced by food habits and food environments, nutritional knowledge, cultural norms and expectations and mass media depictions of what constitutes an ideal figure, in addition to lifestyle differences that affect physical activity. These factors may differ between Western and Eastern European countries [
5,
8,
9]. However, few studies have examined weight and weight perceptions across various European countries. The Health Behaviour in School-Aged Children (HBSC) study, a cross-national survey conducted by the World Health Organization since 1982, has provided information on self-reported weight and weight perceptions among school-aged children [
14,
15]. This study found considerable variation across the studied countries in the prevalence of overweight, trying to lose weight and perceived need to lose weight [
14]. The between-country variation in perceived need to lose weight was not only due to the different prevalences of overweight in participating countries, but also due to between-country variations in perceptions among overweight respondents. For example, overweight boys compared to non-overweight boys were almost 11 times more likely to try to lose weight in Denmark but only 3 times more likely in Russia. This analysis was limited to 11-, 13- and 15-year old school children. Even within this relatively narrow age range, body weight and weight perceptions changed significantly with age [
14]. While HBSC considerably added to the knowledge of weight and weight perceptions among school age children across different countries, less is known about older adolescents and young adults. The International Health and Behaviour Survey (IHBS), which was conducted in 22 countries, reported perceived weight and BMI calculated from self-reportef height and weight for university students [
8]. However, since the samples from participating countries were too small for separate analyses, the results were reported for five regions: Western European countries and the U.S., and Eastern European, Mediterranean, Pacific Asian and South American countries. Our study adds to this literature by providing weight perceptions and self-reported height and weight in student samples from seven European countries with sample sizes large enough for a country-specific analysis.
The aim of this analysis was to compare the relationship between perceived body weight and BMI based on self-reported height and weight in student populations across different European countries, including one Northern European country (Denmark), two Western European countries (Germany, Spain), three Eastern European countries (Poland, Bulgaria, Lithuania) and one South-Eastern European country (Turkey). Of particular relevance are countries that have recently joined the European Union (Bulgaria, 2007, Poland and Lithuania, 2004) and the candidate country Turkey, as these countries are currently undergoing economic and societal transitions with current and projected changes in economic growth. The expected economic development and growing Western European influence may lead to lifestyle changes that may also affect body weight and perceived body weight among student populations in these countries [
9].
Discussion
Male students generally reported a higher BMI than female students, and there was a tendency toward lower BMIs in the Eastern European countries Poland, Bulgaria and Lithuania as compared to the Southern and Western European countries Germany, Denmark and Spain. Samples from the different countries differed substantially with respect to their BMI category distributions. While between 10% and 18% of females and between 18% and 27% of males in the Western and Southern European countries were overweight or obese, the prevalence was substantially lower in the Eastern European countries and in Turkey. We also found large differences with respect to the proportions of students who perceived themselves to be "a little" or "much too fat". Female students in all countries were more likely to describe themselves in this way than male students. Females in Germany, Denmark, and Poland, and males in Germany and Denmark were most likely to describe themselves as overweight. The substantial variation across countries is consistent with findings from the study comparing university students from 22 countries [
8] and with cross-national studies in younger adolescents [
24,
25]. For countries that were included in IHBS as well as in our study (Poland, Germany, Bulgaria and Spain), the self-reported weight, height and BMI agreed very well [
8]. For Lithuania, a 2002 study using measured weight and height reported data for 18-year-old boys and girls matching our findings very well[
26].
When we considered BMI calculated from self-reported data and perceived weight jointly, we found a substantial level of misperceptions regarding body weight in students from European countries. These perceptions regarding body weight as related to BMI consistently differed by gender but were similar across countries. Most female students described their weight as "just right" at a BMI <20 kg/m
2, which is in the low range of normal BMI, whereas most male students described their weight as "just right" at a BMI around 24 kg/m
2, which is in the upper range of normal BMI. In the sensitivity analysis, all corresponding lines were shifted by approximately 0.3 kg/m
2 to the right - leaving all findings described above virtually unchanged. Our analysis differs from the previous analysis conducted by Wardle et al. [
8] who used country-standardised deciles of BMI as the independent variable related to perceived weight in order to avoid using a BMI cut-point. We avoided this problem by treating BMI as a continuous variable in our analysis of association between reported BMI and perceived weight status.
Among Lithuanian students, we observed similar gender differences but an overall higher proportion of students rated their weight as "just right" over a wider range of BMI scores. In Lithuania there were substantially smaller differences in terms of weight, height and BMI between genders than in the other countries; the small differences might result from lower importance of body shape as a measure of attractiveness and subsequently in a less sharp delineation of ideal body weight. While we did not assess ideals of attractiveness in our study, other studies have found that population groups differ in their ideals regarding body weight [
25]. Among German male students, an exceptionally low proportion reported "being just right", and a large proportion considered themselves too fat. Future studies are necessary to confirm these findings and to examine potential explanation for the differences we found.
Apart from the above dissimilarities, our findings suggest that weight ideals are rather uniform across the European countries and different for male and female university students. A multinational study among school-age children displayed a substantial variation in perceived need or attempts to lose weight among overweight boys and girls across 36 countries [
14]. The data are not directly comparable to ours, because only a joint overweight category was reported and differences in weight distribution within this category could introduce additional variation across countries. Nevertheless, assuming a typical skewed distribution of BMI, the results for overweight adolescents should be more similar across countries in the absence of country-specific effects. Therefore, the findings in school-age children (11-, 13- and 15-year olds) appear in some contrast to our findings in university students. One possible explanation is that at younger ages, perceptions are more likely to be shared among peers (and therefore country specific responses exist), while in early adulthood more homogenous perceptions are created by media. Future longitudinal studies are needed to assess this issue. Interestingly, data from the HBSC study also suggest that Lithuanian overweight adolescents are among those with lowest attempts or perceived need to lose weight [
14], which is in agreement with our results.
Females are more likely to perceive a lean body as ideal, which may be fuelled by images of thin women portrayed in the media [
27‐
29]. In a recent study among female college students in the United States, 39% of normal weight students named media as a source of pressure to be a certain weight [
30]. This is a public health concern, because females who restrict their food intake in order to achieve or maintain their desired body weight may have a nutrient intake that is inadequate for optimal health and may develop eating disorders [
4]. In the study by Wardle and colleagues [
8], about 50% of all female students from 22 countries were trying to lose weight, although only 5% had a BMI ≥ 25 kg/m
2. Because several studies have found high rates of problem eating behaviours in university students, prevention programs for high risk female students may be appropriate [
13].
The preference of males for a slightly heavier build may be due to male ideals of being "muscular" [
31,
32] and the absence of positive media portrayals of extremely thin males. The fact that males were more likely than females to rate their weight as "just right" even at higher BMI suggests that they are less likely to perceive themselves as being overweight. Other researchers who studied university students had similar findings: Wardle et al. [
8] showed that the proportion of males who were trying to lose weight was substantially lower than among females. A study by Mintz and Betz [
27] among students in the United States showed that men tended to perceive themselves as normal if they were actually overweight. Studies are ongoing to further examine this drive for muscularity, especially among male students [
28,
33].
Strengths and Limitations
As strength, this study included a relatively large number of students from several European countries. With the exception of Spain, students were not explicitly informed that the survey included questions about weight. Therefore, it is unlikely that students declined participation because of this aspect. Still, there may be a selection bias, because students not interested in the health survey may differ in respect to their weight and their weight perceptions from their peers who participated in the study. Due to the high response rates achieved, this bias seems to be limited in all countries except Spain, where the response rate was substantially lower. However, findings from Spain were well in line with other countries, suggesting that the selection bias related to self-reported weight and weight perception may be similar in all countries included in this analysis.
As in the International Health and Behaviour Survey and the Health Behaviour of School Aged Children studies, our measure of BMI was based on self-reported weight and height. The reliability and validity of self-reported weight and height in different populations has been controversially discussed [
34‐
41]. Most studies found a limited underestimation of BMI but with partly substantial effects on prevalence estimates for BMI categories. A recent review of studies conducted among adolescents in the United States indicated mean differences in self-reported versus directly measured BMI of -2.3 to 0.2 in females and -3.0 to -0.1 in males. While differences between self-reported and directly measured BMI were very small in nationally representative surveys, they were substantially larger in convenience samples or locally-based surveys [
21]. Among other variables, the differences between reported and measured BMI might depend on education and age. An underestimation of 0.98 kg/m
2 in females and 0.75 in males for BMI was found in Greek adolescents [
38]. A recent analysis using German HBSC sample demonstrated that adolescents, especially younger adolescents often do not report their weight or height, possibly because they do not know them [
42]. Large proportions of missing BMI data were found in HBSC samples from many countries as well [
14]. University students could be considered as the population group with more accurate, maybe best possible reporting, given their high education status and age range in early adulthood. In our own validation study in a German sample of students, we found an acceptable agreement between self-reported and measured BMI (mean difference of 0.18 kg/m
2) [
22]. Depending on the distribution of BMI, in some countries the underestimation might affect the prevalence of some BMI categories more than in others, but as demonstrated in the sensitivity analysis, correcting for a homogenous underestimation of weight did not change the qualitative differences observed across countries. More complex assumptions about underreporting of weight and possibly overreporting of height could result in further changes, therefore our estimates of the prevalence of BMI categories should be treated with caution. There could be cultural differences in the accuracy of reported BMI, but our analysis on last digit preferences for self-reported height and weight does not support this notion. On the other hand, the underreporting would affect findings presented in Figure
3 only slightly, lending further support to studies that use self-reported BMI for correlational analyses (in contrast to the estimation of prevalence of overweight) [
43,
44].
As many other studies [
4,
8] have done, we assessed perceived weight using a single question. Future research should use more sophisticated instruments to assess body perceptions with regard to muscularity, height and body fat distribution [
33].
Our data were generated from student samples at one or two universities per country and may not be representative of all students of the respective countries. A comparison with representative data on students' age and gender distribution [
45] confirms that Danish and German students are on average older than students from the other countries that are included in this analysis, and that there are more female than male students. Nevertheless, any distortion of the gender distribution is not likely to affect our results as the analysis was stratified by gender. Finally, the study was not conducted in all countries in the same year and while we do not expect large changes during a five-year period, some changes might have occurred.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
RTM designed the research question, conducted the analysis and drafted the manuscript. AEM wrote the final manuscript. WE, CS, JP and FG participated in writing the manuscript. All authors have read and approved the final manuscript.