Obesity has been associated with negative effects on natural fertility and poor prognosis when assisted reproductive technologies (ART) are performed. Patients attending for fertility treatments are often advised to optimize their weights to improve the outcomes. There is lack of enough information on how weight-loss would be effective for improving fertility in women who are overweight or obese. We conducted a systematic review to evaluate whether weight-loss achieved by lifestyle program improves natural or assisted reproduction in obese infertile women. We searched CENTRAL, MEDLINE, and EMBASE up to March 2018. Two reviews were selected as randomised trials assessing a lifestyle intervention in women with obesity before receiving treatments for infertility and appraised their risk of bias. We extracted data on pregnancy, birth, and miscarriage rates as the primary outcomes and pooled effect estimates using a random effects model. The primary outcome was the live birth rate. We reported summary measures as the relative risk (RR), 95% confidence interval (CI), and percentage of heterogeneity (I2). We included eight randomised trials with 1175 women. Lifestyle programmes, improved pregnancy rates (RR: 1.43, CI: 95% 1.02 to 2.01; I2=60%; 8 RCTs; N=1098) but had no impact on live births (RR: 1.39, CI: 95% 0.90 to 2.14; I2=64%; 7RCTs; N=1034). Our findings suggest that women participating in lifestyle interventions had an increased risk of miscarriage (RR: 1.50, CI: 95% 1.04 to 2.16; I2=0; 6RCTs; N=543). We rated the quality of evidence for these outcomes as the moderate-to-low. Lifestyle interventions slightly increased the pregnancy rate, while it would be uncertain whether it can improve the live birth. Lifestyle interventions can increase the risk of miscarriage. More research is needed to further explore lifestyle interventions on reproductive outcomes in obese infertile women. Instituto de Salud Carlos III