Immobility in childhood can cause early liver damage in adulthood

Children who spend more than six hours a day sitting have a significantly increased risk of developing severe fatty liver disease and cirrhosis of the liver by early adulthood, according to a new study. The findings will be presented at the Endocrine Society's annual meeting, ENDO 2024, in Boston, Massachusetts, and published in Nature's npj Gut and Liver.

"We found that the association between sedentary behavior and liver damage is likely causal," said lead researcher Professor Andrew Agbaje, MD, MPH, PhD, from the University of Eastern Finland in Kuopio, Finland.

“The public needs to be aware of the health risks of a sedentary lifestyle in children, adolescents and young adults,” added Agbaje, who is also based at the University of Exeter in England. “Advanced fatty liver disease and cirrhosis, which are severe scarring and hardening of the liver, can increase the risk of future liver cancer or the need for a transplant.”

Fatty liver disease is a harmful accumulation of fat in the liver. When this condition is not related to alcohol consumption but is associated with one of the components of metabolic syndrome, it is called metabolically associated steatotic liver disease (MASLD).

For this study, Agbaje analyzed data from a large U.K. birth cohort study called the Avon Longitudinal Study of Parents and Children (ALSPAC), or “Children of the 90s.” The study included 2,684 children who had their movements measured repeatedly with an accelerometer worn on their waist from ages 11 to 24. At ages 17 and 24, the participants had liver ultrasounds to assess fatty liver disease and the presence of liver scarring. They also had blood tests to measure liver enzyme levels.

On average, the children in the study spent 6 hours a day sitting or inactive, but this increased to 9 hours a day by early adulthood. As children, they did 6 hours a day of light-intensity physical activity, which offset the harmful effects of 6 hours of sitting.

For every half hour of sedentary behavior above 6 hours per day, the risk of developing fatty liver disease in children increased by 15% by age 25. Increased sedentary time was associated with a 3-hour decrease in time spent in light-intensity physical activity by early adulthood. However, each additional half hour of light-intensity physical activity above 3 hours per day reduced the odds of severe fatty liver disease by 33%.

“We believe that this change in sedentary time compared to light-intensity physical activity sets the stage for disease onset and progression,” Agbaje said.

The prevalence of MASLD was 1 in 40 participants (2.5 percent) at age 17 and 1 in 5 participants (20 percent) at age 24. Agbaje called the finding surprising because the risk of MASLD increased eightfold in just seven years, and a 20 percent prevalence of the disease is not typically seen until the mid-40s.

Half of 24-year-olds with MASLD had severe disease, or significant amounts of excess fat in the liver. One in every 40 young people already had signs of liver scarring, with three in 1,000 young people meeting diagnostic criteria for cirrhosis.

However, he found that engaging in light-intensity physical activity for at least 3 hours a day reversed premature liver damage. Each additional minute of moderate to vigorous physical activity per day was associated with a small reduction in the odds of severe MASLD at age 24, but had no effect on the odds of developing cirrhosis.

“The most effective remedy for the devastating effects of childhood sedentary behavior is not the much-hyped moderate-to-vigorous physical activity of 60 minutes a day,” Agbaje said. “Rather, it is light-intensity physical activity of three to four hours a day.”

Examples of light-intensity physical activity include playing outside, playing on a playground, walking the dog, running errands for a parent, or walking and biking.