A new study suggests there's a link between having heavy sons and cardiovascular death, but having underweight sons appears to be less hazardous than expected.

Previous research has already linked obesity to higher rates of death from cardiovascular disease, diabetes and some kinds of cancer. Studies have also shown that very thin people may be at higher risk of death from conditions such as respiratory disease and lung cancer, but some researchers question those findings.

Whether a person is overweight or underweight is defined using a measurement based on height and weight called the body-mass index (BMI).

In the new study, researchers from the University of Bristol in the United Kingdom and the Karolinska Institute in Sweden looked at more than one million pairs of parents and their young adult sons, checking to see whether the child's BMI predicted the cause of death of their parent.

The researchers found that parents with obese sons were more likely to die of cardiovascular disease, diabetes and some cancers. But no link was seen between low BMI in the sons and higher risks of respiratory disease and lung cancer deaths in the parents.

The findings, published online Dec. 23 in the BMJ, could be used to debunk the notion that obesity doesn't have as much to do with health as had previously been reported, the researchers said.