Abstract and Introduction
With obesity on the rise in the general population, it has also become more prevalent among people of reproductive age. Weight loss has shown benefits in overweight women and men experiencing fertility problems. However, the existing weight-loss interventions for individuals with infertility are associated with high drop-out rates and limited success. In this article, we argue for the development of weight-loss programmes targeting couples, as couples are routinely seen in fertility clinics, rather than individuals. Couples may have correlated weights, and similar eating and activity patterns. Involving both partners may facilitate mutual support, behaviour change, weight loss and programme continuation, at very little additional cost. A successful couple-based intervention could improve the chances of achieving pregnancy and delivering a healthy baby, with a reduction in pregnancy complications. In the longer run, both partners and their baby could benefit from maintained behaviour change with better health across the lifespan. We conclude that there is a need for research to systematically develop a couple-based weight-loss intervention with state-of-the-art design that is tailored to both partners' needs.
With obesity on the rise in the general population (World Health Organization, 2016), it has also become more prevalent among people experiencing fertility problems (Vahratian and Smith, 2009). It is widely recognized that being overweight in the face of central adiposity may contribute to delayed conception. Much of the prevailing literature uses weight and body mass index (BMI) as surrogates for adiposity, and while muscle mass may increase these measures, persons with BMI of 30 kg/m2 or more mostly have excess body fat, as do as many as 50% of those below (Romero-Corral et al., 2008).
In women, insulin resistance secondary to overweight and obesity can disrupt ovulation through its effect on the sex hormone pathway, as well as through leptin and other adipokines (Zain and Norman, 2008; Klenov and Jungheim, 2014; Pantasri and Norman, 2014). Oocyte quality may also be compromised (Klenov and Jungheim, 2014), as embryos derived from the oocytes of obese women have been noted to be of poorer quality (Carrell et al., 2001; Metwally et al., 2007). High BMI may also affect endometrial quality and implantation, as obese recipients of oocytes from normal weight donors are less likely to conceive following in-vitro fertilization (IVF) than normal weight recipients (Bellver et al., 2007).
In men, increased body weight may also compromise fertility. Excessive lower abdominal fat can increase testicular temperature during episodes of prolonged sitting, which may have implications for spermatogenesis (Hammoud et al., 2012). Obese men have been shown to have increased oestrogen levels, with disruption of the hypothalamo-pituitary-gonadal axis (Schneider et al., 1979; Shukla et al., 2014). Such high circulating oestrogen levels have also been shown to have a deleterious effect on spermatogenesis in animal studies (Goyal et al., 2003). In humans, higher BMI and more central adiposity are associated with reduced sperm concentration, lower total motile sperm count (Hakonsen et al., 2011; Hammiche et al., 2012; Eisenberg et al., 2014) and abnormal sperm morphology (Hakonsen et al., 2011; Hammiche et al., 2012). In a systematic review investigating the impact of BMI on sperm parameters (Sermondade et al., 2013) across 21 studies and 13 007 men attending fertility clinics, oligozoospermia and azoospermia were more common among overweight (OR 1.11, 95% confidence interval (CI) 1.01–1.21), obese (OR 1.28, 95% CI 1.06, 1.55) and morbidly obese men (OR 2.04, 95% CI 1.59–2.62) (Sermondade et al., 2013).
Few researchers have studied the association between weight and fertility in both partners. One study of 47 835 couples sought to explore the effect of obesity on couple infertility, over and above the effects on each individual (Ramlau-Hansen et al., 2007). Among couples where both partners were either overweight or obese, the adjusted odds of a delay of over 1 year in achieving pregnancy were 1.41 (95% CI 1.28, 1.56) for overweight and 2.74 (95% CI 2.27, 3.30) for obese couples, compared to normal weight couples, with a dose-response relationship with increasing BMI. Obesity in both partners was associated with greater difficulty achieving pregnancy (Ramlau-Hansen et al., 2007). Another study found that couples where both partners' BMI exceeded 35.0 kg/m2 experienced a delay in time to pregnancy, or reduced fecundity, when compared to couples with a BMI below 25 kg/m2 (adjusted fecundity odds ratio aFOR 0.41; 95% CI: 0.17, 0.98) (Sundaram et al., 2017).
For assisted conception, it would appear that IVF live birth rates (Petersen et al., 2013), but not those with intracytoplasmic sperm injection (ICSI) (Petersen et al., 2013; Wang et al., 2016), might be reduced by couple obesity, though further research seems warranted to confirm whether this is truly the case (Schliep et al., 2015).
Hum Reprod. 2017;32(12):2359-2365. © 2017 Oxford University Press