Obese men are much more likely to be infertile than their healthier counterparts.
They also have have poor quality DNA in their sperm and are more likely to be unsuccessful with assisted reproduction, according to new review.
The University of Adelaide's Joanna Briggs Institute analysed 30 research papers on obesity and male fertility, involving 115,000 men.
The review published in the journal Reproductive BioMedicine Online, found obesity has serious implications for mens' fertility, just as it has for women.
"Our study found that compared to men of a healthy weight, obese men were two thirds more likely to be infertile and almost three times as likely to have a non-viable pregnancy after undergoing assisted reproduction," said lead author Dr Jared Campbell.
There is far less research on the impact of paternal weight than on the impact of maternal obesity on fertility and the health of offspring, he said.
Adelaide University's Dr Michelle Lane said the review showed both men and women should be a healthy weight before trying to conceive a child.
"Men often get let off the hook when it comes to infertility, with women feeling at fault, but this review clearly demonstrates the importance of mens' health in reproduction and pregnancy," she said.