Model and author Lisa be is a firm believer of the mother’s ability to influence the sex of her child.

She realized while researching a book that she had had a diet now associated with the conception of boys.

She now has two after eating what experts say is food high in energy.

"I did eat things like that. I ate bananas, I ate porridge in the morning. I had lots of sushi which meant lots of soy sauce," says Be.

Research carried by the Universities of Exeter and Oxford and in involving 740 first-time pregnant women showed that those who had consumed the most calories, the most nutrients, were more likely to conceive boys.

Over the past 40 years the number of boys born in industrialized countries has been falling.

It means say researchers, skipping breakfast, now increasingly common in the developed world, could be a bad move for those hoping for a son.

"We know that in in-vitro fertilization male embryos are favored by having a high concentration of glucose around them, so it might in a natural diet if the woman for example, skipping breakfast, she may have very low blood sugar in the morning and that may be the reason why boy embryos are selected against," says Dr. Fiona Mathews of Exeter University.

So if you thought it just about the X or Y chromosome, maybe you have to think again.