Overweight and obese persons seeking fertility should be educated on the detrimental effects of fatness and the benefits of weight reduction, including improvement in pregnancy rates. A combination of a reduced calorie diet, by reducing fat and refined carbohydrate intake, and increased aerobic exercise should form the basis of programmes designed for such individuals. A lack of randomized studies in men and couples, and studies evaluating barriers to undertaking weight loss in infertile populations is evident, and future research should examine these issues further.

The prevalence of overweight and obesity in women of reproductive age has increased over the past 30 years. Infertility affects 1 in 7 couples, and female obesity is associated with anovulation. The mechanisms by which excessive fat delays time to pregnancy (TTP) appear rooted in ovulatory problems and direct effects on oocytes, causing poorer embryo development, as well as in effects on the endometrium. Weight loss in women has been shown to improve conception, but not necessarily live birth rates following fertility treatment, and further research in this area is needed. The obesity epidemic has been accompanied by a potential rise in male infertility, which has been attributed to hormonal disturbances and compromised semen parameters.

Summary Being overweight or obese can have a negative impact on fertility outcomes. This systematic review updates randomized controlled trial (RCT) findings on the effectiveness of weight loss interventions in reducing weight and improving reproductive outcomes of women and men with overweight or obesity and infertility. Eligible studies, published since the last review, were identified by searching databases from March 20, 2016 until March 31, 2020. RCTs involving any type of lifestyle intervention were considered. Eight RCTs were identified and aggregated with seven RCTs included in our previous review. Meta‐analyses revealed that women randomized to a combined diet and exercise intervention were more likely to become pregnant, risk ratio (RR) = 1.87 (95% CI 1.20, 2.93) and achieve a live birth RR = 2.20 (95% CI 1.23, 3.94), compared to women in control groups who received no or minimal intervention. This pattern was not replicated in trials where control groups received immediate access to assisted reproductive technology (ART). No eligible randomized trials involving men were identified. Data were largely obtained from small scale studies. Better designed, adequately powered, robust randomized trials are needed to better understand the effect of weight loss interventions on reproductive outcomes in both women and men.

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.