Exercise makes the blood of obese people healthier

20 June 2018. Exercise can reduce inflammation in obese people by changing the characteristics of their blood, according to new research published in The Journal of Physiology.

Obesity is a global health challenge, with approximately one-third of adults affected. Obesity increases the risk of health problems, such as heart disease and type 2 diabetes. Many of the health problems linked to obesity are a result of chronic inflammation. Inflammation is a natural process in the body in response to harm, but in obese people it can become long term and this can lead to damage of healthy tissue. Certain blood cells are more likely to cause inflammation, and if these cells are made in the body in greater numbers than normal they can spread to organs in the body and cause them to malfunction.

The blood cells responsible for causing inflammation are formed from stem cells within the body. This new research is the first to show that exercise alters the characteristics of these blood forming stem cells and therefore reduces the number of blood cells likely to cause inflammation. These findings provide a new explanation of how exercise may improve health in adults with obesity.

Young, lean adults and young, obese adults (who were otherwise healthy) were recruited for this study. Comprehensive physiological characterisation of all participants occurred before and after completion of a six-week exercise program. The exercise program consisted of three bicycling or treadmill running sessions per week with each session lasting approximately one hour. Blood was collected before and after the exercise training intervention to quantify blood-forming stem cells. The results of the study demonstrated that exercise reduced the number of blood-forming stem cells associated with the production of the type of blood cells responsible for inflammation.

The research group is now interested in determining if these changes in blood cell populations improve the function of muscle and fat involved in energy consumption and storage among people with obesity. They are also looking to investigate whether these effects of exercise on blood cells are also seen in other chronic conditions associated with increased inflammation.

Principal Investigator, Dr Michael De Lisio was delighted by the impact the exercise intervention had on some of the participants’ exercise habits:

“This research is important because it helps us understand how and why exercise improves the health of people with obesity.”

“After participating in the exercise intervention, some participants were inspired to participate in our local half-marathon. This enthusiasm for exercise and building the habit of increased physical activity is one of the most rewarding aspects of conducting these types of human exercise trials”.


Notes for Editors

1. Chronic inflammation is characterized by an increase in the content of mature proinflammatory blood cells that can invade tissues throughout the body and cause organ dysfunction. These mature proinflammatory blood cells originate from blood-forming stem cells. Certain proteins on the surface of these blood-forming stem cells can increase their potential to become proinflammatory blood cells and invade into distant organs. Previous work has shown that exercise reduces the content of mature proinflammatory blood cells in obesity. Whether these changes were the result of decreased proinflammatory blood cell production due to alterations in blood-forming stem cells was not known. This new work demonstrates that exercise training reduced the number of blood-forming stem cells expressing these cell-surface proteins associated with increased proinflammatory blood cell production.

2. Limitations: Despite the novel findings of this study, it is important to note the lack of a non-exercised control group means that it is possible that the results observed may have been due to non-exercise related causes. This is a common limitation in human studies, and the research team included several experimental controls (i.e. diet, time of day, etc.) that provide confidence that their findings are indeed due to exercise and not some other factor. Another important consideration, is that both groups of participants (lean and obese) lost weight and fat mass. This makes it difficult to determine if their findings were a direct result of exercise or weight loss.

3. Link to full paper: Effects of Endurance Exercise Training on Inflammatory Circulating Progenitor Cell Content in Lean and Obese Adults: https://physoc.onlinelibrary.wiley.com/doi/10.1113/JP276023

4. The Journal of Physiology publishes advances in physiology which increase our understanding of how our bodies function in health and disease. http://jp.physoc.org

5. The Physiological Society brings together over 3,500 scientists from over 60 countries. The Society promotes physiology with the public and parliament alike. It supports physiologists by organising world-class conferences and offering grants for research and also publishes the latest developments in the field in its three leading scientific journals, The Journal of Physiology, Experimental Physiology and Physiological Reports. www.physoc.org 


The Physiological Society: 
Andrew Mackenzie, Head of Policy and Communications
+44 (0)20 7269 5727

Research institution:
Véronique Vallée
University of Ottawa, Media Relations Officer

Corresponding author:
Michael De Lisio, Ph.D. 
University of Ottawa,