April 3 (HealthDay News) -- People whose fathers had early-onset obesity are at increased risk for elevated liver enzyme levels and liver disease, says a U.S. study.

Researchers evaluated 1,732 children, average age 42, of participants in the Framingham Heart Study, a long-term study of families in Framingham, Mass. The researchers found that people whose fathers were clinically obese at an early age were more likely to have increased liver enzyme (serum alanine aminotransferase -- ALT) levels, an indicator of liver disease.

When the researchers conducted a secondary analysis that didn't include obese offspring, they still found a strong link between elevated serum ALT levels and paternal early-onset obesity. This demonstrates that the link between obesity in the father and elevated serum ALT levels in children is independent of the offspring's body-mass index (BMI) and persists among non-obese children, the researchers said.

No relationship was found between early-onset obesity in mothers and ALT levels in their children.

"These findings show that familial factors may play a role in elevated serum ALT levels in the general population," study senior author Dr. Caroline S. Fox, medical officer with the Framingham Heart Study, said in a prepared statement.

The study was published in the April issue of Gastroenterology.

Serum ALT levels are a marker of liver disease in the general population, and previous studies have shown that there's a strong link between obesity and elevated serum ALT levels, according to background information in the study.

Up to 7 percent of the adult U.S. population has unexplained elevated ALT serum levels, according to the U.S. National Health and Nutrition Examination Survey. These elevated ALT serum levels may be due to nonalcoholic fatty liver disease (NAFLD), which is believed to be the most common cause of elevated ALT serum levels, which can lead to inflammation of the liver (hepatitis), scarring of the liver (cirrhosis), and liver cancer.

"Serum ALT elevations and NAFLD are more prevalent than ever in the U.S., though we don't know specifically what's causing the increase. Our results point to a genetic connection between early-onset paternal obesity and increased ALT levels," Fox said.

"This study is the first to look at the connection between parental early-onset obesity and elevated serum ALT levels in their children using objective clinical measurements of parental BMI instead of self-reports," study first author Dr. Rohit Loomba, of the Liver Diseases Branch of the U.S. National Institute of Diabetes and Digestive and Kidney Diseases, said in a prepared statement.

"Though we are looking at a very specific, community-based sample in our work, the results suggest an association between elevated serum ALT levels and early-onset paternal obesity. Additional studies are needed to assess whether this connection suggests a genetic predisposition to developing liver disease in larger populations," Loomba said.

SOURCE: American Gastroenterological Association, news release, April 1, 2008