Women who fall pregnant while dieting are more likely to have a child that could become obese or diabetic in later life, a study suggests.

Researchers found in a study on sheep that giving ewes less food at the time of conception caused DNA changes in the brains of their young.

The University of Manchester scientists suspect the findings may hold true for humans as well and could explain why twins are more likely to develop Type 2 diabetes in adulthood.

The study investigated twin pregnancies in sheep as well the pregnancies of ewes that received less food around the time the lamb was conceived.

The researchers then looked at tissues from the brains of the unborn lambs to see if there were changes in the structure of the DNA.

Study leader Anne White said: 'We found that unborn twin lambs had changes in the structure of DNA in the region of the brain that regulates food intake and glucose that resulted in an increased chance of diabetes in adulthood.

'Our findings provide a reason why twins are more likely to get diabetes but we have also shown that mothers who don't have enough food around the time of conception may have a child who grows up with an increased risk of obesity.'

The researchers believe their findings are relevant to humans as they reveal a non-genetic, or 'epigenetic', way in which the DNA of offspring can be altered.

Professor White added: 'Our study is important because it shows that factors in the brain can be altered by non-hereditary mechanisms and this results in changes in the body, which could make people obese.

'The findings may provide a new understanding of why twins can develop diabetes and also suggests that dieting around the time a baby is conceived may increase the chance of the child becoming obese later in life.'

More and more people are becoming obese and getting diabetes, while rates of twins are steadily increasing as women have babies at older ages and rates of conception using artificial reproductive technologies increase.

Dieting in young women is also very common and can occur in women who may not know they are pregnant.

The team's findings in sheep, if replicated in humans, suggest that obesity and diabetes could be more likely in twins and in children from mothers who aren't eating properly, or dieting, around the time of conception.

Researchers say it could affect the advice giving to women who are planning a family to reduce future health risks for their children.

The study was published in the Journal of the Federation of American Societies for Experimental Biology.