Regular exercise is well known to benefit health, but scientists are still working to understand exactly how those benefits appear inside the body. In a new study, researchers identified changes in the metabolic and immune systems that distinguished adults who exercised regularly from those who reported no physical activity.

The findings, published September 18 in Science Advances, point to a potential biological pathway through which exercise may help manage chronic conditions such as type 2 diabetes, heart disease and cancer. The study can be read in the original research paper.

Study analyzed blood samples from 400 adults

The research team analyzed data from the China Immunology Multiomics Atlas, or CIMA. The dataset includes blood samples and detailed lifestyle questionnaires from 400 adults.

To capture the clearest differences between activity levels, the researchers focused on participants who reported either the most or the least exercise. The active group exercised at least three times per week, completing at least 150 minutes of moderate-intensity activity or 75 minutes of vigorous-intensity activity during that time. The sedentary group reported that they were unable to exercise at all.

The researchers examined blood markers linked to metabolism, including blood sugar and fat levels. People who exercised more showed increased sugar and fat metabolism, stronger muscle metabolism and signs of greater physical activity.

Their blood also contained more antioxidant molecules, which help fight processes that can damage cells.

Multi-omics revealed exercise-related cellular changes

The scientists used a multi-omics approach, combining data from several biological systems. These included metabolites, which are byproducts of metabolism; fats; proteins; and RNA, a molecule that helps cells build proteins.

The team also studied chromatin accessibility, a feature of DNA that influences whether genes can be switched on. DNA is wrapped into structures called chromatin. When chromatin is more accessible, genes are easier for cells to read, transcribe and use to produce proteins.

By combining these types of data, the researchers were able to examine how immune cells from regularly active people differed from those of sedentary participants. The analysis revealed several changes in immune-cell activity.

Exercise may prime immune cells to respond to threats

Exercise participants showed enhanced activity in cytotoxic T cells and natural killer cells, both of which help identify and destroy threats in the body.

Naive immune cells—unspecialized reserves that can later develop into active immune cells—also showed greater chromatin accessibility in genes involved in fighting threats. This suggests that these cells may have been more prepared to respond when needed.

The researchers observed changes in monocytes and B cells as well. These cells help alert other parts of the immune system to potential threats. In people who exercised regularly, genes associated with these warning signals were more active.

Overall, the findings suggest that regular physical activity may prime the immune system to respond to potential threats. Previous research has linked inactivity with an increased risk of chronic health conditions, including type 2 diabetes, while exercise is associated with a lower risk of those conditions.

What the study cannot prove

The study had several limitations. The researchers did not record the specific types of exercise participants performed, only how often and for how long they exercised. They also had limited information about the participants’ physical characteristics.

Because the study compared people with different lifestyles, it could not prove that exercise directly caused the changes in metabolism or immune activity. It is also possible that the immune systems of sedentary participants were less active for other reasons, which may have contributed to their inability to exercise.

Dr. Michael Sievers, a researcher at the University of Duisburg-Essen who was not involved in the study, said many of the links between exercise and these biological systems were already known. The advance, he said, was the detailed analysis of what happens inside individual cells.

“This is a really good paper, showing for the first time what’s actually happening at the intercellular level when you play sports,” Sievers said.

Despite its limitations, examining the cellular basis of exercise’s effects could help researchers better understand why physical activity supports overall health.

This article is for informational purposes only and does not provide medical advice.

Source: Song, X., Lv, J., Ge, S., Xu, S., Wu, Y., Zheng, Y., Zhou, W., Li, L., Zhang, Y., Zhang, J., Chen, Z., Gao, P., Ying, P., Ying, J., and Liu, C. (2026). “Multi-omics profiling identifies molecular and cellular signatures of periodic movement in human peripheral blood.” Science Advances, 12(38).