How men lose weight could affect their chances of having a baby, with new research from the University of Adelaide revealing healthy lifestyle behaviors seem more beneficial for improving fertility than weight loss itself.
Researchers analyzed the results of 32 studies across the world involving men with obesity between the ages of 18 and 50 who were undergoing weight loss interventions such as bariatric surgery, weight loss medications or diet and exercise programs.
“Obesity is a modifiable cause of male infertility. Preconception guidelines often talk about maintaining a healthy weight but there is very little information available on which weight loss method is best for men for infertility,” said first author Dr. Andrew Peel from the University of Adelaide’s Freemasons Center for Men’s Health and Wellbeing and Robinson Research Institute.
“This study was the first comprehensive analysis to look at the reproductive effect of multiple obesity interventions on sperm in men, and whether the amount of weight lost makes a difference. The available data primarily examined sperm parameters such as motility, concentration, and morphology. The absolute degree of weight loss did not directly correlate with changes in sperm parameters.”
The review, published in Human Reproduction Update, showed men who underwent bariatric surgery lost substantial weight quickly but didn’t experience any notable, positive changes to sperm parameters such as volume, concentration, motility and DNA damage.
There was also some evidence to suggest that surgery could have short-term detrimental effects on reproduction, possibly due to nutritional deficiencies or increased exposure to endocrine-disrupting chemicals—a side-effect of rapid weight loss.
In contrast, the few studies examining lifestyle interventions that focused on improving diet and exercise did result in improvements to sperm quality, even with modest weight loss. “Lifestyle changes are associated with modest improvements in sperm motility and morphology, even though the amount of weight lost was much smaller than surgical options,” said Dr. Peel.
“This indicates that for men with obesity, while obesity has detrimental effects, reproductive success may be more dependent on optimizing nutrition and exercise rather than substantial weight loss alone.”
The data on weight loss medications was limited and mainly related to the use of Metformin and Liraglutide. “There is an urgent need for research on newer weight loss drugs like Ozempic to see what impact they have on male fertility. This is even more pressing given the rising popularity of these medications,” said senior author Dr. Nicole McPherson from the University of Adelaide’s Robinson Research Institute.
“Up to 30% of Australians aged 25–45 years live with obesity. Previous research has shown that infertility rates are approximately 50% higher in men with obesity compared to men of a normal weight, with the condition associated with reductions in basic sperm parameters among other reproductive issues,” said co-senior author Professor Gary Wittert from the University of Adelaide Freemasons Center for Male Health and Wellbeing.
Dr. McPherson added, “We are not only living at a time when obesity is considered to be an epidemic, but fertility levels are also at record lows. There is a real knowledge gap when it comes to the best approach for men with obesity wanting to improve their fertility and we strongly advocate for more research in this area to establish optimal preconception recommendations for men.”
More information:
Andrew Peel et al, The effect of obesity interventions on male fertility: a systematic review and meta-analysis, Human Reproduction Update (2025). DOI: 10.1093/humupd/dmaf025
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