Scientists in Australia have found a link between obese fathers and diabetes in their children.
Researchers from the University of New South Wales fed male rats a high fat diet so they developed diabetes, then mated them with healthy female rats.
The rats then gave birth to babies with pre-diabetes.
Researchers think the poor diet altered the male rats' sperm, causing diabetes in their offspring, the ABC reports.
It is too soon to know if the same thing would occur in humans. However, the study's author, Professor Margaret Morris, says the findings are significant.
She suggests men should think more carefully about their diet and exercise before having children.
"If it's true in the human, it really underlines the necessity for both parents to be approaching pregnancy in the best possible physical shape."
Researchers say the study will help them understand how diseases are passed from one generation to another.