A beer belly does slash your chances of becoming a father

A beer belly reduces a man’s chances of becoming a father by almost half, a study suggests.

Harvard research shows that every extra two inches on a man’s waist cut his odds of having a baby by nearly 10 per cent.

And a pot belly was found to be especially dangerous.

experts warned that fat produces a chemical that turns testosterone into the female sex hormone oestrogen.

Professor Charles Kingsland, clinical director of Care fertility clinics, said: ‘Pot-bellied men, beware.’

US doctors weighed and measured almost 180 men and women before they started IVF.

every two-inch (5cm) increase in a man’s middle cut his partner’s chances of having a baby by 9 per cent at each IVF attempt, a medical conference heard. This means a man whose waist wobbled in at 40 inches was a third less likely to become a father than one with a trim 32inch tummy.

beer bellies were particularly problematic. An additional two inches on the waist of a man of normal weight – but with a spare tyre – reduced his chances by 46 per cent. The figures stood even when other information, including the man’s age and whether he smoked and the woman’s age and weight, was factored in.

researcher Dr Jorge Chavarro said that flab stored around the middle pumps out more harmful chemicals than other fat.

He told the european Society for Human reproduction’s annual conference that it is not just women who need to prepare for pregnancy.

Dr Chavarro, of the Harvard School of Public Health in boston, said: ‘These results highlight that reproduction is a team sport and focusing exclusively on women may obscure an important part of the picture.’

Around one in seven couples have trouble conceiving and male infertility is to blame about half the time. Two-thirds of adults in the UK are overweight or obese. The average man’s waistline is 38.2 inches (97.1cm ) – 1.5 inches bigger than in 1993.

Fertility experts said the warning about beer bellies doesn’t just apply to men having IVF. Obese men are more likely to be impotent and they make less sperm. Their sperm is also poorer at swimming and its DNA more damaged.

Sheena Lewis, a fertility expert at Queen’s University belfast, said that aromatase, an enzyme made by fat, can turn testosterone, which is key to sperm production, into oestrogen.