Body Size at Birth and Same-Sex Marriage in Young Adulthood

Abstract

An unexplained excess of overweight has been reported among lesbians. In contrast, reports suggest that gay men may be, on average, slightly lighter and shorter than heterosexual men. We studied associations between weight, length, and body mass index (BMI) at birth and same-sex marriage in young adulthood among 818,671 Danes. We used linear regression to calculate differences in mean body measures at birth and Poisson regression analysis to calculate confounder-adjusted incidence rate ratios (IRR) of same-sex marriage according to body measures at birth. Overall, 739 persons entered same-sex marriage at age 18-32 years during 5.6 million person-years of follow-up. Birth year-adjusted mean body measures at birth were similar for same-sex married and other women. However, same-sex marriage rates were 65% higher among women of heavy birth weight (IRR = 1.65; 95% CI = 1.18-2.31, for > or =4000 vs. 3000-3499 g, p = .02), and rates were inversely associated with birth length (p (trend) = .04). For same-sex married men, birth year-adjusted mean weight (-72 g, p = .03), length (-0.3 cm, p = .04), and BMI (-0.1 kg/m(2), p = .09) at birth were lower than for other Danish men. Same-sex marriage rates were increased in men of short birth length (IRR = 1.45; 95% CI = 1.01-2.08, for < or =50 vs. 51-52 cm), although not uniformly so (p (trend) = .16). Our population-based findings suggest that overweight in lesbians may be partly rooted in constitutional factors. Novel findings of smaller average body measures at birth in same-sex marrying men need replication. Factors affecting intrauterine growth may somehow influence sexual and partner-related choices in adulthood.

Born This Way: Using Intrinsic Disorder to Map the Connections between SLITRKs, TSHR, and Male Sexual Orientation

“…These observations, especially those associating hyperthyroidisms with homosexuality in men, seem to support the prenatal androgen model linking same‐sex attraction in men to under exposure to prenatal androgens, and in women, to overexposure. This model also seems to align with reports of lower body weights and heights on average among homosexual men and higher average body measurements among homosexual women, both at birth and in adulthood …”

Birth weight and two possible types of maternal effects on male sexual orientation: A clinical study of children and adolescents referred to a Gender Identity Service

“…One study found that men who entered same-sex marriages showed lower body size at birth compared to other men (Frisch & Zdravkovic, 2010), but this study did not examine body size at birth in relation to birth order. One study found that men who entered same-sex marriages showed lower body size at birth compared to other men (Frisch & Zdravkovic, 2010), but this study did not examine body size at birth in relation to birth order.…”

“…Several studies have considered birth weight in relation to sexual orientation. One study found that men who entered same-sex marriages showed lower body size at birth compared to other men (Frisch & Zdravkovic, 2010), but this study did not examine body size at birth in relation to birth order. Consistent with the hypothesis that fraternal birth order-induced maternal immune responses are associated with homosexuality in males, homosexual men who had one or more older brothers exhibited lower birth weight (Blanchard & Ellis, 2001).…”

Theories and etiologies of sexual orientation.

“…In a U.S. national sample of young people, lesbian and bisexual women as compared with heterosexual women were heavier, and the difference was apparent in adolescence (Austin et al, 2009). A Danish study, however, did not support the hypothesis of weight differences in puberty because women who married women were heavier at birth than women who married men, suggesting that the weight disparity was possibly attributed to prenatal rather than pubertal hormones (Frisch & Zdravkovic, 2010). The remaining and prevalent studies have no bearing on the hypothesis because they focus on sexual-orientation disparities in adulthood and not on BMI differences during adolescence (i.e., puberty).…”

“…Homosexual men are shorter than heterosexual men (Bogaert, 2010). The hormonal effect may occur prenatally, at least for some men, rather than during puberty, however, because the Danish study found that men who married men were more likely than men who married women to be shorter in length at birth (Frisch & Zdravkovic, 2010).…”