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Obesity is a disease that can increase the risk of other health issues, such as diabetes and cardiovascular events. According to a new study, researchers used a newly developed biomarker of aging to measure the effects of obesity on the liver. Based on the results gathered by this epigenetic clock, the team found that obesity could speed up the liver's aging process.

"This is the first study that evaluated the effect of body weight on the biological ages of a variety of human tissues," study first author Steve Horvath, a professor of human genetics at the David Geffen School of Medicine at UCLA (University of California, Los Angeles) and a professor of biostatistics at the UCLA Fielding School of Public Health, said. "Given the obesity epidemic in the Western world, the results of this study are highly relevant for public health."

The international team composed of researchers from UCLA and the University Hospital Dresden in Germany used the epigenetic clock, which was developed by Horvath, to examine the effects of excess weight on the body's tissues. They analyzed roughly 1,200 human tissue samples with 140 of them being liver samples. The team measured the biological age of the select tissues.

The researchers compared the tissues' biological age to the chronological age of the subjects. In lean subjects, both ages matched. In obese participants, however, the biological age of the liver tissue samples was higher than the chronological age of the subjects. Horvath calculated that for every 10-unit increase in body mass index (BMI), which measures obesity, the liver's epigenetic age increased by 3.3 years.

"This does not sound like a lot, but it is actually a very strong effect," Horvath said reported in the press release. "For some people, the age acceleration due to obesity will be much more severe, even up to 10 years older."

The team noted that obesity did not affect the epigenetic age of the body's fat, muscle or blood tissue. Bariatric surgery (weight-loss surgery) did not reverse these signs of aging in the short-term. The researchers stressed the importance of maintaining a healthy weight.

"The increased epigenetic age of liver tissue in obese individuals should provide insights into common liver-related comorbidities of obesity, such as insulin resistance and liver cancer," the authors wrote. "These findings support the hypothesis that obesity is associated with accelerated aging effects and stresses once more the importance of maintaining a healthy weight."

The study was published in the journal, Proceedings of the National Academy of Sciences (PNAS).