Fat fathers may be more likely to produce sons and daughters who struggle with weight, a study suggests.
Scientists saw the trend in mice whose fathers had grown obese after being fed a high fat diet.
They believe a similar effect may occur in humans and are investigating the biological processes involved.
The research points to altered activity levels of inherited genes that speed up or slow down metabolism.
In the study, affected offspring mice put on extra weight from six weeks of age despite being fed a healthy low-fat diet.
Male mice also had different patterns of body fat composition - which can affect disease susceptibility - from mice with normal weight fathers.
"We've identified a number of traits that may affect metabolism and behaviour of offspring dependent on the pre-conception diet of the father," said study leader Dr Felicia Nowak, from Ohio University in the US.
Only male mouse parents were given the high fat diet. Mother mice were fed low fat meals and were not overweight.
Previous research linking parental obesity with childhood weight gain in humans has focused on mothers rather than fathers.
The findings were presented today at the annual meeting of the Endocrine Society in San Francisco, US.
A surprise from the research was that as well as being weight-prone, offspring of obese male mice were unusually physically active.
At six weeks old, male offspring voluntarily ran more, as did their sisters at six months.
The behaviour may represent an attempt to burn off extra fat and reduce the risk of diabetes and heart disease, the researchers believe.
In the next phase of the study, the team will try to identify the genes responsible for the physiological and behavioural changes.
"Early detection and prediction of risk for obesity, diabetes and related diseases will enable individuals and health care workers to delay or prevent the related disabilities and increase life expectancy," said Dr Nowak.