‘Being too fat can damage sperm’

What did the media report?

The media reported that obese men have poorer quality sperm, which scientists suggest may be caused by fat around the testicles causing them to heat up.

What did the research show?

The stories were based on UK research presented earlier this month at the annual conference of the European Society of Human Reproduction and Embryology in Barcelona.

An observational study compared results of seminal fluid analysis from 5,316 men attending Aberdeen Fertility Centre with difficulties conceiving – of which there were complete BMI datasets for 2,037. Subjects were divided into four categories based on their BMI, with possible confounding factors, such as smoking, alcohol intake and age, taken into account.

Researchers found men in the category with an optimal BMI – 20-25, as classified by the World Health Organization – had higher levels of normal sperm and higher semen volume than those in other groups. No difference was noted in sperm concentration or motility.

However, there was no control group to compare the effect of male BMI in fertile and infertile couples to see if the poorer semen quality correlated with reduced fertility.

What did the researchers say?

‘Our findings were quite independent of any other factors, and seem to suggest that men who are trying for a baby with their partners should first try to achieve an ideal body weight, said study author Ghiyath Shayeb, a researcher at Aberdeen University’s department of obstetrics and gynaecology.

‘The mechanism for the relationship could be a number of things – different hormone levels in obese men, simple overheating of the testicles caused by excessive fat in the area, or that the lifestyle and diet that leads to obesity could also lead to poorer semen quality. We just don’t know the answer yet, but this is an important question that needs urgent attention.’

What does this mean for nursing practice?

Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield and secretary of the British Fertility Society, said: ‘There are now a number of good studies to show that increased BMI in men can be associated with poor sperm production. It would therefore be sensible for anyone trying to conceive to get their BMI into the normal range.’

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