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

Following a study carried out using sheep, University of Manchester scientists believe the findings may hold true for humans as well.

The research may also have found a reason why human twins are more likely to develop type-2 diabetes later on in life.

The team investigated twin pregnancies in sheep, as well as 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 that would alter genes involved in food intake and glucose levels after birth.

Professor of endocrine sciences 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 research, carried out with colleagues in New Zealand and Canada, is published in the Journal of the Federation of American Societies for Experimental Biology.

Although conducted on sheep, the researchers believe their findings are relevant to humans too as they reveal a non-genetic or "epigenetic" way in which the DNA of offspring can be altered.

While the study does not have implications for the treatment of diabetes or obesity, the researchers say it could be important for disease prevention regimes whereby advice on eating is given to women who are planning a family that could reduce future health risks for their children.

Professor White added: "This is not an inherited change in the genes but a change in the structure of the DNA that affects the genes, and therefore much more unusual.

"What is significant is that the changes we have found are in genes that control food intake and glucose levels and alterations in these genes may lead to obesity and diabetes.

"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."

These findings come on the same day as the NHS revealed they are trialing controversial treatment that gives unborn babies diabetes drugs in the womb to prevent them being born obese.

In a world’s first trial of its kind, the trial is aimed to slash obesity rates right from inside the womb and the first moment the baby is born as obesity among pregnant women reaches epidemic proportions.

The metformin drug, which has been used by diabetics for many years and lowers the levels of insulin in the bloodstream, has been medically approved to use during pregnancy. It’s believed that it will reduce the fatty deposits around the unborn baby’s liver and organs.

So far, the trial funded by the Medical Research Council, has involved 400 obese pregnant women in Liverpool, Coventry, Sheffield and Edinburgh and it’s likely to expand elsewhere in the UK within the next five years.

Professor Jane Norman from Edinburgh University, who led the research, said in a statement: “One of the challenges is that many women feel perfectly healthy but there is very good evidence that women who are obese have an increased risk of pregnancy problems and their babies are at risk, and we'd like to reduce that risk.”