For obese people, working out can change more than their appearance. Recent research shows it can also reduce inflammation by changing the characteristics of their blood.

Many health problems linked to obesity are a result of chronic inflammation, which can lead to tissue damage. Now, researchers at the University of Illinois have found that exercise can fundamentally alter certain blood cells responsible for inflammation and reduce their numbers.

The researchers studied two groups of people, separating them according to lean and obese body mass. Their physical traits were measured before and after a six-week exercise program that included three bicycling or treadmill running sessions a week, each one lasting an hour. Blood samples were collected before and after the exercise to measure the number of blood-forming stem cells where inflammation originates.

Exercise reduced the number of stem cells that generate the blood cells responsible for damaging inflammation, the researchers found. The study participants also improved their cardiorespiratory fitness and reduced their body fat percentage.

The research is significant, the team noted, because it helps explain how and why exercise improves the health of obese people.

Next, they want to know whether changes in the makeup of blood cells can improve muscle function and how fat is consumed and stored by people who are obese. They also want to determine if the effects of exercise on blood cells are also seen in other chronic conditions affected by inflammation.

So if you’re looking to shed some pounds with exercise, keep trying. You’re not just improving your appearance, but also bettering your blood.