Being overweight at 18 to 20 years old may signal that a man is headed for severe liver disease decades later, according to a large, long-term study from Sweden.

Researchers followed more than 44,000 men conscripted for military service in 1969 and 1970, and found those who were overweight as young men were 64 percent more likely to have serious liver problems and liver-related deaths in the next 40 years compared to normal weight counterparts.

"Most likely, these teens already had non-alcoholic fatty liver disease (NAFLD) at the start of the study, or developed it down the road," said lead author Dr. Hannes Hagstrom of the Center for Digestive Diseases at Karolinska Institute in Stockholm. "We know that some persons with NAFLD do develop severe liver disease."

The researchers used national records on 44,248 Swedish men conscripted for military service, which requires a full physical exam, and tracked their health outcomes in medical registries up to 2009.

By that time, 393 men had been diagnosed with severe liver disease, including reduced liver function, cirrhosis or liver-related death. Those who were overweight as teens were at the greatest risk, even after the analysis accounted for alcohol and tobacco use, according to the report in Journal of Hepatology.

About 7 percent of the men had been overweight in their youth, meaning they had a body mass index (BMI) between 25 and 29.9. BMI is a measure of weight relative to height, and the range between 18.5 and 24.9 is considered normal. BMI of 30 or above is considered obese.

The highest risk for severe liver disease later on in life was alcohol consumption of more than 3.5 bottles of wine per week, Hagstr'm noted.

"However, it is already known that alcohol causes liver disease," he told Reuters Health by email. "What's new here is that being overweight/obese was associated with an increased risk independent of how much alcohol these young men were drinking.

"Other significant risk factors were smoking, use of narcotics, self-rated health, cardiovascular fitness and high blood pressure," Hagstrom said.

The results would likely have been similar for women but that's not necessarily clear in this study, he said.

A similar study of men conscripted into military service in Sweden, published in the European Heart Journal, found that young men at the high end of the normal BMI range may have a higher risk of heart failure later in life compared to their peers at the low end of normal BMI.

"Those in high normal range don't need to be concerned because (heart failure) is still very rare," said lead author Dr. Annika Rosengren, professor of medicine at the Sahlgrenska Academy in Gothenburg. "The absolute risk is still very low."

More on this...

But in Sweden, heart failure is becoming more common among people younger than 45, and may continue to do so as overweight also increases, she told Reuters Health. Younger people with heart failure are frequently misdiagnosed as having asthma, since both can cause shortness of breath, she said.

"There's already an incentive to try to decrease the obesity epidemic, this is just another reason for doing it," she said.