The effect of weight loss interventions for obesity on fertility and pregnancy outcomes: A systematic review and meta-analysis

BackgroundWeight loss could improve fertility, perhaps by reducing insulin resistance. ObjectivesTo assess the effect of weight loss interventions on fertility in women with obesity not recruited because of known infertility. Search StrategyThree databases during 1966-2020, trial registry. Selection CriteriaRandomized controlled trials (RCTs) with a follow-up of 1 year or more, with a mean cohort BMI of 30 kg/m(2) or above. Data Collection and AnalysisA systematic review and meta-analysis was conducted. The primary outcome was pregnancy. The secondary outcome was weight change. Main ResultsA total of 27 RCTs (5938 women) were included. Weight loss interventions showed no statistically significant increase in pregnancies compared to control interventions (24 trials, 97 women with pregnancy; risk ratio [RR] 1.43, 95% confidence interval [CI] 0.91-2.23); weight change (mean difference [MD] -2.36 kg, 21 trials, 95% CI -3.17 to -1.55). Compared with low-fat diets, very-low-carbohydrate diets showed no statistically significant effect on women with pregnancy (three trials, 14 women with pregnancy; RR 1.37, 95% CI 0.49-3.84) or weight change (MD -0.32 kg, 95% CI -3.84 to 3.21). ConclusionsDiet-based weight loss interventions for women with obesity not recruited because of infertility were effective at producing long-term weight loss. The effects on fertility were not statistically significant, but few trials provided data. Weight loss trials should routinely collect fertility outcomes. Systematic review registrationPROSPERO CRD42017078819.