Relations with the opposite sex are important social interactions in the lives of adolescent girls. A growing literature has focused on determinants and consequences of adolescent sexual activity, and this body of work has generated much knowledge. However, the predominant focus has been on vaginal intercourse, whereas in reality teenagers engage in a variety of different sexual activities. For example, recent findings from the National Survey of Family Growth indicate that 54% of adolescent girls aged 15-19 in the United States in 2002 had ever performed oral sex (Lindberg, Jones, and Santelli 2008), that 11% of this same cohort had ever engaged in anal sex (Lindberg, Jones, and Santelli 2008), and that 10% of teen females have had heterosexual oral sex but not vaginal intercourse (Mosher, Chandra, and Jones 2005). Additionally, many studies in the existing literature focus on questions involving the timing of sexual debut or whether individuals abstain from sexual intercourse. That is, they generally do not distinguish between sexual intercourse that is particularly risky (e.g., unprotected sex with multiple partners) and that which confers much less health risk (e.g., protected sex within an exclusive relationship). The former is far from rare. For example, reports based on the 2002 and 2003 Youth Risk Behavior Surveys indicate that 11% of 9th-12th grade girls reported having had four or more sexual partners and that 17% of sexually active 15-19-year-old girls reported that they did not use contraceptives at their most recent sexual encounter (Abma et al. 2004; Kaiser Family Foundation 2005).
Many sexual activities confer health risks and females bear the brunt of most of those risks. It is well known that unprotected vaginal intercourse is strongly associated with unintended pregnancy and sexually transmitted diseases (STDs). According to Landry and Turnbull (1997): (1) Women are more susceptible to STDs than men when they have sex with an infected partner and do not use a condom. (2) Infected women are more likely than infected men to be asymptomatic, which can lead to serious health complications. (3) With the exception of human immunodeficiency virus (HIV), STDs may have more life-threatening consequences for women (e.g., pelvic inflammatory disease, ectopic pregnancy, and cervical cancer) than for men. (4) Young women contract STDs more easily than adult women because they have fewer protective antibodies and because cervical immaturity facilitates the transmission of infections. Recent evidence from the Centers for Disease Control indicates that one in four young women between the ages of 14 and 19 in the United States is infected with at least one of the most common STDs (human papilloma virus [HPV], chlamydia, herpes simplex virus, and trichomoniasis) (CDC 2010). Having multiple sexual partners is an important risk factor for STDs because many teenagers do not use condoms correctly and consistently (Santelli et al. 1998). Oral sex can also lead to transmission of STDs and most teens do not use barrier protection during oral sex (Halpern-Felsher et al. 2005). Finally, studies have found that anal intercourse among adolescents and young adults is often unprotected (Lescano et al. 2009; Rotheram-Borus, Marelich, and Srinivasan 1999) and that it is associated with high STD risk among young heterosexual women (Jenness et al. 2011).
Overweight has become a pressing public health issue in the United States and most other developed countries, and there is much research and policy interest in its causes and consequences. Teenage girls have not been spared from the obesity epidemic. Between the 1960s and 2003-2005, the prevalence of overweight in girls aged 12-19 in the United States increased from 4.7% to over 17% (National Center for Health Statistics 2010, Table 73). A few studies in the economics literature have investigated the role of overweight as a determinant of adolescent sexual behavior, which is viewed through a lens of assortative mating in a market for sexual partners. …