How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence.

The prevalence of obesity is increasing worldwide, with a corresponding increase in overweight and obese patients referred with infertility. This systematic review aimed to determine whether non-surgical weight reduction strategies result in an improvement in reproductive parameters affected by obesity, e.g. delayed time to pregnancy, oligozoospermia and azoospermia. No prior reviews have examined this within the general fertility population, or in both sexes.

Our objective was to answer the question: 'In overweight and obese women, men and couples seeking fertility treatment, what non-surgical weight-loss interventions have been used, and how effective are they at weight loss and improving reproductive outcomes?'

An electronic search of MEDLINE, EMBASE and the Cochrane Library was performed for studies between January 1966 and March 2016. Text word and MESH search terms used related to infertility, weight and barriers to weight loss. Inclusion criteria were an intervention to change lifestyle evaluated in any study design in participants of either gender with an unfulfilled desire to conceive. Studies were excluded if they included participants not attempting pregnancy, with illnesses that might cause weight fluctuations, or studies evaluating bariatric surgery. Two reviewers performed data extraction and quality assessment using the Cochrane Risk of Bias Tool for randomized trials, and a ratified checklist (ReBIP) for non-randomized studies.

A total of 40 studies were included, of which 14 were randomised control trials. Primary outcomes were pregnancy, live birth rate and weight change. In women, reduced calorie diets and exercise interventions were more likely than control interventions to result in pregnancy [risk ratio 1.59, 95% CI (1.01, 2.50)], and interventions resulted in weight loss and ovulation improvement, where reported. Miscarriage rates were not reduced by any intervention.

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.