Obesity decreases sperm quality

Obese men have poorer quality sperm, perhaps because too much fat around their testicles causes them to heat up, scientists have suggested. Researchers from the University of Aberdeen in Scotland looked at men in 2 000 couples who were having difficulty conceiving. The heaviest men had the highest proportion of abnormal sperm. Speaking at a European fertility congress, the researchers said that losing weight would probably improve fertility.

The men were divided into four groups, according to their BMI (body mass index).

Other factors which could affect fertility, such as smoking, high alcohol use and age, were taken into account by the researchers.

Men who had a healthy BMI of 20 to 25 were had higher levels of normal sperm than those who were heavier.

They also had higher semen volume, the European Society for Human Reproduction and Embryology meeting in Barcelona was told.

But those with a higher BMI had lower volumes of seminal fluid, and a higher proportion of abnormal sperm.

Other studies have also linked obesity to DNA damage in the sperm.

It is already known that overweight women have more difficulty conceiving.