Obese men should consider losing weight if they want to have children, British researchers say, after finding that men with a higher body mass index (BMI) had lower volumes of seminal fluid and a higher proportion of abnormal sperm. The new findings were presented by Dr. A Ghiyath Shayeb, from the University of Aberdeen, at the annual conference of the European Society of Human Reproduction and Embryology. The results are based on seminal fluid analysis of 5,316 men attending Aberdeen Fertility Centre with their partners for difficulties in conceiving. The scientists divided the men into four groups according to their BMI, from being underweight to being considerably overweight. They then looked for a relationship between BMI and semen quality. The analysis showed that the men who had an optimal BMI (20-25, as classified by WHO), had higher levels of normal sperm than those in the other groups. They also had higher semen volume. There was no significant difference between the four BMI groups in sperm concentration or motility.
The researchers did not look at DNA damage in the sperm, preferring to look at the parameters of the routine semen analysis, which all men attending the fertility centre will have at least once. "Other studies have suggested an association between male obesity and increased DNA damage in the sperm, which can be associated with reduced fertility as well," noted Shayeb.
"Our findings were quite independent of any other factors," he added, "and seem to suggest that men who are trying for a baby with their partners, should first try to achieve an ideal body weight. This is in addition to the benefit of a healthy BMI for their general well being."
The team intends to follow up their research by comparing male BMI in fertile and infertile couples to see if the poorer semen quality correlates with reduced fertility. "There has been a significant rise in the numbers of men with poorer semen parameters in the industrialized world," said Shayeb, "but this has not been reflected so far in male infertility. To compare male BMI in these two groups therefore seemed to us to be a logical next step."
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Source: European Society for Human Reproduction and Embryology
