Medical researchers have for the first time shown a link between a father's weight and diet at the time of conception and an increased risk of diabetes in his offspring.

The finding, reported in the journal Nature, is the first in any species to show that paternal exposure to a high-fat diet initiates progression to metabolic disease in the next generation.

"We've known for a while that overweight mums are more likely to have chubby babies, and that a woman's weight before and during pregnancy can play a role in future disease in her children, partly due to the critical role the intrauterine environment plays in development," said study leader Professor Margaret Morris, from UNSW's School of Medical Sciences.

"But until now, the impact of the father's environment -- in terms of his diet -- on his offspring had not been investigated." The work formed the basis of the PhD study of Dr Sheau-Fang Ng, who showed that paternal environmental factors such as diet and weight are important contributors to disease in the next generation.

In the Nature study, male rats were fed a high fat diet to induce obesity and glucose intolerance and then mated with normal weight females. The resulting female offspring exhibited impaired glucose tolerance and insulin secretion as young adults.

"This is the first report of non-genetic, intergenerational transmission of metabolic consequences of a high fat diet from father to offspring," Professor Morris said.

"A family history of diabetes is one of the strongest risk factors for the disease; however until now, the extent of any influence of non-genetic paternal factors has been unclear."

Professor Morris said the research showed that overweight fathers can play a role in "programming" epigenetic changes in their offspring, possibly through effects on their sperm caused by their consumption of high-fat food. Epigenetics is a process whereby changes in gene expression -- and hence function -- can occur even when there are no alterations in the DNA sequence.

Professor Morris said the study expands our understanding of the role environmental factors might play on a child's physiology and metabolism.

"It adds another level to our understanding of the causes of the growing epidemics in obesity and diabetes," she said. "While here we studied female offspring, we need to examine whether the effect is also found in males."

The work was carried out in collaboration with scientists in the UNSW Schools of Medical Sciences and Biotechnology and Biomolecular Sciences, the Garvan Institute, and the University of Adelaide.

Professor Morris will present the findings at the Australia and New Zealand Obesity Society meeting in Sydney.