Study Reveals Surprising Sex Differences in Fat Metabolism

A groundbreaking study from the Molecular Transducers of Physical Activity Consortium (MoTrPAC) has uncovered unexpected differences in how exercise affects fat metabolism in males and females. The study, published in Nature Metabolism, is the largest to date to explore the molecular actions that translate vigorous movement into numerous health benefits.

Extensive Effects of Exercise on the Body

The MoTrPAC study, involving more than 100 scientists across over two dozen sites in the United States, found that the effects of exercise are extensive, affecting more than 35,000 molecules. The study subjects were rats, which share much of their basic physiology with people, and the findings are now being used as a starting point to investigate what happens in humans.

“Everyone knows that exercise is good for you, but no one knows exactly why,” said Joshua Adkins, a scientist at the Department of Energy’s Pacific Northwest National Laboratory and a corresponding author of the study. “We don’t know what’s happening in the body that creates such great benefits.”

The team looked at 18 tissue types and blood, finding molecular signals in both males and females that demonstrated extensive benefits of exercise, such as enhanced liver function, stronger heart muscle, enriched immunity, and reduced inflammation in the lungs and gut.

Striking Differences in Fat Metabolism Between Sexes

The most remarkable difference between the sexes was in the fat tissue. The study found that fat tissue between males and females is very different, even in sedentary animals. However, the sex-dependent responses to exercise were truly striking.

“Males burn fat for energy while females preserve their fat mass. This is brought about by many differences in molecular responses lurking beneath the surface in fat from male compared to female rats. The dichotomy is truly striking,” said Christopher Newgard, a corresponding author and director of the Duke Molecular Physiology Institute.

Exercise made the fat stores of both sexes healthier—more metabolically active and energetic, with fewer signals like those involved in obesity. This was more noteworthy in the male rats, whose fat was less healthy to start.

“We saw both sexes mobilize their metabolism to get the energy they need,” said first author Gina Many. “But they get their energy in different ways. Females do so without drawing much from their fat stores, likely because those are critical to reproductive health.”

The investigators said the results make it crucial that health studies include women and men, noting that when it comes to exercise, many more men than women have been studied.

“This study really opened my eyes,” said Newgard. “The differences between the sexes are much more vast than I would have anticipated. This is changing the way I am approaching other studies, including one on insulin resistance in males and females. These findings provide a road map for those experiments.”

Keyword/Phrase: Sex Differences in Exercise Fat Metabolism

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