International Journal of Obesity https://doi.org/10.1038/s41366-020-0524-8 REVIEW ARTICLE The effect of body mass index on sperm DNA fragmentation: a systematic review and meta-analysis Mahdi Sepidarkish 1 ● Arezoo Maleki-Hajiagha 2 ● Saman Maroufizadeh 3 ● Mahroo Rezaeinejad 4 ● Amir Almasi-Hashiani 5 ● Maryam Razavi 1,6 Received: 12 June 2019 / Revised: 11 December 2019 / Accepted: 3 January 2020 © The Author(s), under exclusive licence to Springer Nature Limited 2020 Abstract Background Current evidence supports the association between the high sperm DNA fragmentation (SDF) and the poor fertilization rate following either natural conception or assisted reproductive techniques (ART). On the other hand, there are conflicting results regarding the decreased sperm DNA integrity in men with high body mass index (BMI). Objective We aimed at the present systematic review and meta-analysis at evaluating the association between BMI and SDF. Methods We searched databases of Medline, Embase, Scopus, and Web of Science up to May 2019, to identify obser- vational studies that assessed the associations between BMI and SDF. BMI was classified, according to the standard BMI classifications, into six categories including underweight (<18.5), normal weight (18.5–24.99), overweight (25–29.99), class I obesity (30–34.99), class II obesity (35–39.99), and class III obesity (≥40). Standardized mean differences (SMDs) and 95% confidence intervals (CIs) of SDF were calculated by using a random-effects model for BMI categories. Results The initial extensive literature search yielded 33,739 potentially relevant articles (3,917 from Medline, 781 from Embase, 12,685 from Scopus, and 9,348 from Web of Science). Fourteen studies (nine cross-sectional, four cohort, and one case–control studies), with a total number of 8,255 participants, were included in the meta-analysis. Finally, three studies reported higher SDF levels in obese men (BMI = 30–34.99) compared with normal-weight men (BMI < 25) (SMD: 0.23, 95% CI: 0.01, 0.46, P = 0.05, I 2 = 0%), but there was no difference between other categories. Conclusions There is insufficient data to demonstrate a positive association between BMI and SDF. Our findings provide a rationale for conducting further cohort studies for evaluation of the association between BMI and SDF, considering potential confounders. Introduction It has been proven that the high level of sperm DNA fragmentation (SDF) (≥30%) reduces fertilization and pregnancy rates following either natural conception or assisted reproductive techniques (ART) [1]. The main etiology of SDF is complex and still unclear, but it can be caused by defects in spermatogenesis following testicular and post-testicular injuries like toxins, hyperthermia, oxi- dants, and hormonal disorders [2]. Obesity is one of the potential lifestyle factors that can increase oxidative stress (OS) levels and consequently DNA damage, in different body organs [3, 4], including testis and germinal cells [5]. * Maryam Razavi dr.razavi351@gmail.com 1 Infertility and Reproductive Health Research Center, Health Research Institute, Babol University of Medical Sciences, Babol, Iran 2 Research Development Center, Arash Women’s Hospital, Tehran University of Medical Sciences, Tehran, Iran 3 School of Nursing and Midwifery, Guilan University of Medical Sciences, Rasht, Iran 4 Department of Obstetrics and Gynecology, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran 5 Department of Epidemiology, School of Health, Arak University of Medical Sciences, Arak, Iran 6 Pregnancy Health Research Center, Department of Obstetrics and Gynecology, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran Supplementary information The online version of this article (https:// doi.org/10.1038/s41366-020-0524-8) contains supplementary material, which is available to authorized users. 1234567890();,: 1234567890();,: