The fatter you are, the more likely you are to be prone to infertility as a guy.

A research study presented at the Endocrine Society’s annual meeting in Atlanta last week is calling for better body weight control in childhood and adolescence in order to stave off infertility later in life.

With male infertility increasing and sperm count dropping by half over the last 40 years, this is a problem.

The study made a link between testicular volume and sperm count. In other words, smaller balls produce less sperm.

According to the study, a quarter of young men aged 18-19 have smaller than normal testicles and this comes against the background of increasing childhood obesity.

“This evidence suggests a possible link between childhood obesity and the high prevalence of low testicular volume in youngsters,” said lead researcher of the study Dr Rossella Cannarella of the University of Catania in Italy.

The study found that children and youngsters who are overweight, or have high levels of insulin, tended to have smaller testicles compared with those who carried a normal weight.

“More careful control of body weight in childhood and adolescence may help to maintain testicular function later in life,” said Cannarella.