A review study published in the Annals of Internal Medicine looks at the effect of weight loss before IVF on reproductive outcomes.
Prof Ying Cheong, Professor of Reproductive Medicine and Honorary Consultant in Reproductive Medicine and Surgery, University of Southampton, said:
“We already know weight loss can help with fertility, but whether it improves IVF outcomes is far less certain. This review sheds some light, but most of the studies are small and at high risk of bias, so the results need cautious interpretation. IVF bypasses many obesity-related barriers, but what is still unclear is if delaying treatment for weight loss truly boosts success rates.
“This review of 12 trials found that weight loss before IVF was linked to higher overall pregnancy rates, mainly from unassisted conception, but the effect on live birth rates with assisted conception was uncertain. Whilst the pooled results look statistically significant, many individual interventions showed no benefit at all. Grouping very different approaches together risks comparing apples and pears, and leaves us unsure which, if any, are genuinely effective before IVF.”
Prof Bassel Wattar, Associate Professor of Reproductive Medicine and Medical Director of the ARU Clinical Trials Unit, Anglia Ruskin University, said:
“The study presented by Michalopoulou and colleagues provides interesting insights into the potential benefits of weight loss interventions for optimizing both natural and assisted fertility outcomes with assisted conception. While the findings indicate some promising signals, they must be interpreted with caution due to several methodological limitations. Notably, the majority of the included trials were characterized by small sample sizes and a high risk of bias. Additionally, there was considerable heterogeneity among the study populations, and four of the included trials excluded women with a body mass index (BMI) above 35—precisely the subgroup most likely to benefit from such interventions. Also, it’s only a modestly greater chance in absolute terms of fertility in the weight loss group, even though the reported odds are high, due to the small sample size included in this meta-analysis.
“Current evidence suggests that women with anovulatory infertility, particularly those with polycystic ovary syndrome (PCOS), may experience a resumption of natural fertility following substantial weight loss (5–10% of body weight). However, these findings remain limited by the paucity of adequately powered trials and insufficient data on live birth outcomes. This meta-analysis highlights the inconsistency in the available evidence and underscores the need for further research, particularly to determine whether intensive weight loss interventions – such as GLP-1 agonists or high-intensity dietary regimens (though it is important to note that GLP-1s are not recommended to be taken during or when trying for a pregnancy) – can restore natural fertility and reduce reliance on assisted conception methods. Furthermore, many patients are currently disadvantaged by the BMI threshold (<30) required to access assisted conception treatments within the NHS in the UK. Establishing reliable, safe, and effective weight loss interventions could enable thousands of patients to access timely IVF treatments and achieve healthier pregnancies with reduced risks. Nevertheless, additional data are required to fully assess the benefits of these interventions during pregnancy and beyond.”
Dr Channa Jayasena, Associate Professor / Consultant in Reproductive Endocrinology, Imperial College London, said:
“Obesity is one of the most common fertility problems for women. It can disrupt periods, and how the ovaries and womb work. Obesity is also a major cause of pregnancy complications. According to the National Institute for Health and Care Excellence (NICE) recommendations, women with obesity are not eligible for NHS funding of fertility treatments such as IVF.
“This study has analysed the results from several studies which looked at whether weight loss improved the chances of pregnancy in women. Weight loss prior to fertility was associated with greater chances of becoming pregnant (either naturally or with IVF treatment). However, it is not clear whether IVF itself became more effective after weight loss.
“Weight loss improves virtually every aspect of health, so this study is a great illustration of its potential benefits for women affected by obesity. It is also important to consider that average weight loss in the analysed studies was achieved under 1 stone (5kg) – this means that achievable levels of weight loss may be enough to improve chances of women with obesity becoming pregnant. Unfortunately, obesity is most likely to affect the poorest in society, so weight loss offers might help disadvantaged couples have a baby when other avenues like IVF are not open to then.”
‘The Effect of Weight Loss Before In Vitro Fertilization on Reproductive Outcomes in Women With Obesity’ by Moscho Michalopoulou was published in the Annals of Internal Medicine at 22:00 UK time on Monday 11 August 2025.
DOI: 10.7326/ANNALS-24-01025
Declared interests
Prof Ying Cheong: “No COI to declare.”
Prof Bassel Wattar: “No conflict of interest to declare.”
Dr Channa Jayasena: “No conflicts.”