Experts link male obesity to infertility

Men with beer bellies were today told to diet or risk never having children after experts found a direct link between obesity and male infertility.

Men who are overweight have higher than average levels of abnormal sperm, which can prevent couples conceiving and also cause miscarriage.

A major study of more than 5,000 men shows that obesity is more damaging to fertility than other lifestyle factors, including smoking and drinking as well as age or social class.

It is already known that obesity is to blame for infertility in women but this is the first time it has been proven to affect a man's ability to have children. The research was carried out by Dr Ghiyath Shayeb, who said that different hormone levels in obese men and the impact of excess fat "overheating" the reproductive organs were both possible reasons for sperm defects.

Dr Shayeb, from the University of Aberdeen, said: "Our findings were quite independent of any other factors [ including DNA damage in sperm] and seem to suggest that men who are trying for a baby with their partners should first try to achieve an ideal body weight."

The Aberdeen findings also showed that men with a higher body mass index - their height to weight ratio - had lower than average volumes of seminal fluid, which is crucial for successful reproduction.

A separate study shows diabetes also has a direct impact on male fertility.

Research by Queen's University in Belfast reveals that the excess sugar produced by diabetics in their bodies causes DNA damage to sperm.

This damage is associated with low quality of embryos, childhood cancers and reduced rates of pregnancy. There has been a significant rise in the number of people diagnosed with in the UK with diabetes, and this is as a direct result of increased levels of obesity.

Both the Aberdeen and the Belfast study were presented today at the European Society of Human Embryology and Fertility conference in Barcelona.

The UK has the third highest rate of fertility treatment in Europe. Figures from the European Society show that 41,911 cycles were carried out in Britain in 2005, with doctors in only France and Germany treating more patients.