In this descriptive study, we found a number of associations between all three weight indices (BMI, perceived weight and weight misperception) and adolescent sexual behaviors with the pattern of associations varying by race/ethnicity. There were no differences in the likelihood of ever having sex based on BMI or weight perception accuracy; however, girls who perceived themselves as overweight were less likely to have ever had sex. In general, sexually-active girls who were or who perceived themselves to be at the weight extremes as well as those with weight misperceptions were more likely to report engagement in sexual risk behaviors compared to normal weight peers or those who perceived their weight to be about right. Moreover, early coitarche, having ≥ 4 lifetime partners, and not using condoms at last sex were the most consistently observed associations. The fact that these associations were not uniform across racial/ethnic groups may have important implications for adolescent health promotion or intervention programs.
Relatively few studies have examined the relationship between body weight and ever having had sexual intercourse.(4
) With few exceptions,(21
) studies have consistently shown overweight individuals are less likely to have ever had sex compared to their normal weight peers.(4
) However, previous studies were conducted among adult(22
) or college-age samples(4
). To our knowledge, prior to this study, associations between weight and having ever had sex among high school-aged students had not been assessed. In contrast to the previous studies, we found no association between BMI and having ever had sex among high school girls. However, having ever had sex did appear to be associated with girls' perception of themselves as overweight.
Previous studies examining the relationship between body weight and sexual risk behaviors focus primarily on young, college females. Wiederman(5
) found no relationship between BMI and number of sexual partners among sexually-active females. Eisenberg(3
) noted that sexually-active students with higher BMI were more likely to have casual or multiple sex partners and report alcohol use at last sex. The only association we noted between BMI and sexual risk behaviors was that sexually-active high school girls with low BMI were less likely to report condom use at last sex compared to their normal weight peers, a finding not previously noted. Our findings indicate that for sexually-active high school girls, sexual risk behaviors may be more common among those with low BMI. This is in contrast to sexually-active college females for whom sexual risk behaviors appear more common among those who are overweight.
Two other important study findings were the associations between perceived weight or weight misperception and engagement in risk behaviors among sexually-active girls. Girls who perceived themselves as overweight were more likely to report coitarche before age 13 and not using a condom at last sex. Similarly, girls with overweight misperceptions were also less likely to report condom use at last sex. There is a paucity of data examining the relationship between either girls' perceived weight or weight misperception and engagement in sexual risk behaviors.(6
) However, prior studies have examined the relationship between other weight-related psychosocial constructs, namely body image(3
) and body satisfaction(5
), and sexual risk behaviors. Poor body image and dissatisfaction with one's body are similar constructs to perceived weight and weight misperception with both likely reflecting individuals' internal assessment of their physical attributes relative to perceived cultural standards. Similar to our findings, these studies have consistently found that women with a poor body image or greater body dissatisfaction are less likely to negotiate sexual encounters (e.g., use condoms) with partners.(3
) Although the directionality of these associations cannot be determined from available cross-sectional data, we speculate that girls with a negative body perception may have a limited capacity or willingness to effectively negotiate with partners resulting in higher rates of sexual risk behaviors. Our data support this by demonstrating that associations between weight-related psychosocial constructs and sexual risk behaviors appear relatively soon after sexual debut. This is an important area for future research because ineffective sexual negotiation increases STI and unintended pregnancy risk. It is important to note that our self-reported weight misperception variable is not meant to label girls as having cognitive pathology requiring clinical assessment and treatment. Rather, it is meant to highlight the fact that adolescent girls' weight and sexual behaviors are related in ways that reflect social and cultural scripts and that the latter may need to be considered in approaches to sexual health education and prevention.
We noted marked racial/ethnic differences in the pattern of sexual behaviors associated with each of the three weight indices. This suggests the mediators of these relationships may operate differentially across racial/ethnic groups. This conclusion is supported by literature demonstrating marked racial/ethnic variations in girls' acceptance of their body size as well as differences in body image, body satisfaction, self-esteem, and male partner's preferences, particularly between Black and Caucasian girls.(28
) Compared to Caucasians, Black girls and their partners are generally more accepting of larger body types.(3
) There is scant literature for other adolescent racial/ethnic groups. The observed racial/ethnic differences also indicate that girls at the weight extremes from different racial/ethnic backgrounds engage in different patterns of sexual risk behaviors. This suggests that sexual education programs may need to be tailored to address how cultural norms regarding body size may influence adolescent sexual decision making.
This study has several strengths. We used a large, nationally representative dataset. However, there was still a relatively small proportion of non-whites. We used several body weight indices to compare the role of BMI, perceived weight and weight misperception on sexual behaviors. Studies of weight misperception and adolescent risk behaviors, especially sexual behaviors, are uncommon.(6
) Finally, we assessed racial differences in the observed association between body weight and girls' sexual behaviors, which has not been previously examined extensively.
This study has several important limitations. The YRBS survey has a cross-sectional design that allows investigators to identify associations but does not allow one to determine causal factors underlying observed relationships. However, the growing body of literature(3
) demonstrating associations between weight and sexual behavior reinforces the validity of our results. The YRBS survey relies on self-reported data. Thus, the data are subject to reporting bias; however, the questionnaire has been evaluated and found to have good test-retest reliability and the estimates of adolescent sexual behavior and condom use are comparable to other surveys.(35
) The survey's reliability and validity for self-reported height and weight is also good and is described in detail elsewhere.(14
) The YRBS data are designed to produce nationally representative estimates for students attending high school but may not reflect behaviors of high-school-age girls not attending school. The condom, contraceptive, and alcohol-use variables were based on last sexual intercourse during the previous three months and, therefore, may not reflect girls' behavior during more distant sexual acts or with regular sexual partners. Finally, although the YRBS questionnaire contains information on a wide variety of risk behaviors, few explanatory variables are included. Thus, we were unable to control for other factors known to confound both sexual behaviors(36
) and weight(39
), such as socio-economic status, body image, self-esteem, family factors, and age.