Everyone gets sick sometimes. But it’s always been my experience that the more in shape I get, the less often I get sick. And it’s fairly common knowledge that exercising regularly boosts your immune system. But what does that mean exactly?

I recently read a fascinating article in the New York Times all about a mice study that’s helping scientists understand how regular exercise can actually keep us from getting sick.

The study, which was published in the Scientific Reports journal in November of this year, examines how obesity, exercise, and inflammation affect how mice get sick and how they recover. The scientists believe that the results from the mice study will translate directly to how humans get sick and recover, as well. Dr. Yoonkyung Park, a professor of biomedical science who oversaw the mice study told the Times, “We strongly believe that long-term, regular exercise can considerably improve the immune defense mechanism against viral infections such as colds and the flu.”

So, how does it all work? In simplest terms, whenever our bodies are confronted with an injury or infection, they respond with inflammation. Inflammation is the body’s way of combatting the germs or injury. Inflammation can help our bodies to heal, but it can also hurt.

Interestingly, people who are obese and carry a lot of fat cells often have low levels of chronic inflammation. Fat cells produce a substance that actually causes inflammation. And too much inflammation that lingers for too long can cause tissue damage and long-term health problems. Additionally, when a body is busy dealing with chronic inflammation, it doesn’t have as many resources to fight off other invading germs or bacteria, making it more prone to sickness and infections. Therefore, obese people tend to get sicker and sick more often than those who aren’t. And obesity and inflammation and the body’s response to it was what interested the scientists in the study.

In the study, researchers separated mice into two groups. One group was sedentary, the “no-exercise” group. The second group of mice were put on a 5-day-a-week swimming regimen for three weeks and labeled the “exercise” group.

Then inflammation levels were studied in both sets of mice during that three week period. As expected, the no-exerecise mice had more fat cells and chronic low levels of inflammation. The exercising mice had spikes in inflammation after exercise, during the healing time when tissues damaged by exercise were being repaired. In the meantime, the number of fat cells in the exercising mice were dropping.

After three weeks both set of mice were injected with a staph infection, a notoriously drug-resistant infection that causes inflammation and infection of bodily tissues. In humans, staph infections can cause sores and lung problems.

Both sets of mice got sick. But the no-exercise mice got way, way sicker and had a hard time recovering. The exercising mice got sick and then recovered.

It turns out that the sedentary mice who had chronic levels of inflammation were unable to recover from the extra inflammation that the staph infection introduced. Their systems were too overwhelmed and weakened. But the exercising mice, who’s bodies were used to fighting inflammation and recovering did just that. After three weeks of exercise they also had fewer fat cells and much lower levels of chronic inflammation. Additionally, according to the Times, the exercising mice made more of a “potent type of antimicrobial immune cell”, which acts like “internal Purell” and “directly kills germs, especially in their lungs”.

Wow! Here is the proof that exercising regularly can keep our bodies healthy. Exercise teaches our bodies how to deal with inflammation. Exercise lowers our fat cell count, which also reduces levels of inflammation. And finally, exercising bodies produce antimicrobial immune cells. When we become stronger, we are actually protecting our bodies from the inside out.

Isn’t the human body amazing? Do you find that you’re healthier when you find the time to exercise regularly? Do you workout with me on a daily basis? If so, have you found that you get sick less often than before you worked out with me?