How Exercise Fights Inflammation

From jogging to weightlifting, physical activity is good for you, in part because it helps your body fight inflammation.

Now, a new review explains exactly how exercise works to lower inflammation. Inflammation is the body's way of healing itself after an injury and protecting itself from infection; but chronic inflammation is linked with all kinds of diseases, from diabetes to heart disease. When you start exercising and moving your muscles, your muscle cells release a small protein called Interleukin 6, or IL-6, which appears to play an important role in fighting inflammation.

IL-6 has several anti-inflammatory effects, including: Lowering levels of a protein called TNF alpha, which itself triggers inflammation in the body. Inhibiting the signaling effects of a protein called interleukin 1 beta, which triggers inflammation that can damage the cells in the pancreas that produce insulin. The biggest factor in determining how much IL-6 your muscles release is the length of your workout — the longer your workout, the more IL-6 is released, according to the review of relevant research.

For example, after a 30-minute workout, IL-6 levels may increase fivefold, but after a marathon, the levels may increase by a factor of 100, according to the review. IL-6 levels peak around the time you finish a workout, and then rapidly decrease back to pre-exercise levels.

A study published in 2003, and part of the new review, explored the role of IL-6 in reducing inflammation. In that study, the researchers injected participants with a molecule from E. coli bacteria that is known to activate the body's inflammatory response. The researchers found that, indeed, when they injected this molecule, there was a two- to threefold increase in levels of the inflammation-triggering protein TNF alpha. But if participants engaged in 3 hours of stationary cycling before the injection, they experienced an increase in their IL-6 levels, and they did not see a similar rise in TNF alpha. This study and others show that a single bout of exercise induces a strong anti-inflammatory effect that appears partly due to IL-6, the review said.

Still, the review acknowledges that IL-6 is likely not the only factor involved in exercise's anti-inflammatory effects. For example, studies have found that regular exercise increases levels of another protein, called Interleukin-15 (IL-15), in muscle cells. IL-15 appears to help regulate the accumulation of abdominal fat, with higher levels of IL-15 providing protection against abdominal fat buildup in mice, the review said. Since abdominal fat itself is thought to promote inflammation, reducing abdominal fat levels may be another way exercise fights inflammation, the review said. The review concludes that exercise should be used as part of the treatment for chronic diseases involving inflammation.

"Physical activity represents a natural, strong anti-inflammatory and metabolism-improving strategy with minor side effects, and should be integrated in the management of patients with chronic diseases," such as type 2 diabetes and cardiovascular disease, the review said.