A recent study published in Cell has found that the liver size of mammals grow by nearly 50% when they are active and feeding. The researchers noted that the liver, which plays an essential role in metabolism and toxin elimination, reaches its optimum efficiency during physical activity and feeding.

A team of researchers at the University of Geneva and the University of Lausanne in Switzerland together with Nestlé Institute of Health Sciences examined the liver activity in mice models. They have found that the organ responds to the body’s feeding and fasting cycles, as well as the variations of day and night within 24 hours. Before returning to its normal dimensions, the liver size in mice has shown to increase by nearly half. The results revealed that the mechanism disappeared when normal biological rhythm was reversed. The experts noted that circadian rhythm disruptions due in part to professional constraints or private habits may potentially affect the liver’s functions.

Mammals have adapted to diurnal and nocturnal circadian rhythms through a central biological clock located in the brain, according to the researchers. Nocturnal rhythms, which reset at daylight, was found to coordinate the subordinate clocks seen in most of our cells. Experts were also able to observe that more than 350 liver-related genes involved in metabolism and detoxification were expressed in a circadian fashion that follows a 24-hour biological rhythm. According to UeliSchibler, Professor Emeritus at the Department of Molecular Biology of the University of Geneva Faculty of Science, most of these genes were influenced by food intake and physical activity patterns.

What The Animal Study Found

Depending on the body’s activity, the research team found that the size of liver cells changes back and forth. However, the activity was only observed in the liver and not in other organs.

Flore Sinturel, author of the study reported in Science Daily that:

“In rodents following a usual circadian rhythm, we observed that the liver gradually increases during the active phase to reach a peak of more than 40 percent at the end of the night, and that it returns to its initial size during the day.”

Results further revealed that the number of liver ribosomes, organelles responsible for generating proteins needed for various liver functions, fluctuated together with cell size. According to Sinturel, the cell size, in order to ensure optimal protein production at night, adapted to the production and assembly of new ribosomes. During the resting phase, excessive ribosome components were then determined, labeled, and broken down.

Moreover, it was found that feeding and fasting cycles influenced liver oscillation. The liver size is affected by the diurnal and nocturnal phases. When feeding phases were no longer responsive to the biological clock, fluctuations in liver size disappeared.

Study co-director Frédéric Gachon noted that:

“The size of the liver and the hepatocytes, as well as their contents in ribosomes and proteins, remain nearly stable when mice are fed during the day. Yet, these animals ingest similar amounts of food, irrespective of whether they are fed during the night or during the day.”

The research team said that factors such as rotating shifts, night works, and frequent international travels are some of the reasons why many people no longer follow their bodies’ circadian rhythm. The people’s present lifestyle can possibly be affecting the liver’s function. Furthermore, experts commented that the next step is to examine whether a similar mechanism is occurring in humans and whether the liver’s biological function is influenced by the same mechanism.