You have probably noticed that a training plan that works for a friend does not always work the same way for you.
Men and women often respond differently to the same workout.
New lab research points to one of the places where that difference may begin.
In a study in rats published in Cell Reports in June 2026, researchers at the University of Missouri found that endurance exercise rewires the liver differently in males and females.
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Female livers made more of the proteins their cells use to produce energy.
Male livers mostly tweaked proteins they already had.
The team tracked liver changes after 1, 2, 4, and 8 weeks of treadmill running in male and female rats, with 5 animals per group.
The work drew on the MoTrPAC consortium, a large research effort that maps the molecular signals set off by physical activity.
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In plain terms, females added new mitochondrial proteins, while males chemically modified the ones already there.
Both routes supported the same goal, better energy production inside the liver cell.
What changed in the liver after 8 weeks
Both sexes picked up real benefits. Markers of liver scarring, known as fibrosis, dropped in males and females alike after 8 weeks.
Both groups also made more cholesterol and bile acids in the liver, which is part of how the body clears fat and cholesterol.
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In males, liver fat levels fell significantly after 8 weeks. Males also pushed more cholesterol and bile acids out of the body through the gut.
In females, those liver fat changes were not seen in the same way, but blood lipids improved.
Why the liver sits at the center of this story
The liver stores and burns fat for the rest of the body.
When too much fat builds up inside it, the condition is called metabolic dysfunction-associated steatotic liver disease, or MASLD.
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According to the American Association for the Study of Liver Diseases, MASLD is the most common chronic liver disease in the world, affecting more than 30 percent of the global population.
Severe cases can lead to cirrhosis or liver cancer.
That is why researchers care which molecular tools the liver reaches for when a person exercises.
If those tools differ between the sexes, treatment advice may need to differ too.
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What this means for your own workout
The findings are in rats, not people, so they are not a prescription.
They are an early signal that one-size-fits-all exercise advice may miss how different bodies respond.
The current message still holds. Regular aerobic exercise helps the liver in both sexes, and clinical guidelines point to aerobic training as a core part of lifestyle care for fatty liver disease.
Sex-based patterns in training have shown up before, including in work on the best time of day to exercise based on your sex.
The Missouri team said the next step is to work out why male and female livers choose different molecular routes, with the aim of guiding more precise care for people with MASLD.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.