Have you noticed that the most physically active and fit people you know never seem to get sick? They appear to breeze healthily through cough and cold season with nary a sniffle, and what’s worse, they tell you it’s because they’re so darn fit.
And as much as you’ll hate to admit it, you’re going to have to give them that. It turns out that better physical fitness does actually lower the number and severity of colds, according to a recent study. Dr. David Nieman, director of the human performance laboratory at Appalachian State University, and his team studied 1,000 adults for 12 weeks during the 2008 winter season, and found that those who exercised more than five times a week had 43% fewer upper respiratory infections than those who were more sedentary. But even more important, says Nieman, is that those who reported being more fit than others of their age had 46% fewer infections than those who admitted they weren’t in great shape. (More on Time.com: How Not to Get Sick)
“Of all the factors we looked at, including age, gender, education level, body weight, diet, mental stress and others, physical activity and fitness ended up being the most powerful predictor of sick days,” says Nieman.
Why? While the study itself didn’t investigate the metabolic reasons for the association, previous work hints that exercise, especially moderate exercise, can increase circulation of the body’s sentry immune cells whose job is to patrol the body and nab any potential viral or bacterial invaders. The more these cells are circulating and on duty, the more likely they will be able to dispatch the first cold or flu agents before they can establish an infection. “If they keep doing that, it all adds up to improved protection against the agents that can make you sick,” says Nieman. (More on Time.com: Fitness Tech: 10 Cool Ways to Get in Shape)
But there is a tipping point to this benefit. Ask marathoners or other extreme athletes, and they will tell you that after a draining event, they are more likely to come down with a cold or the flu. That’s because intense physical activity can stretch the body’s immune system to its limit, leaving cells more vulnerable to infection.
That could be why the current study found that those who were more fit were the least likely to get sick, since they had the most efficient immune systems that were able to effectively recognize and eliminate viruses and bacteria. (More on Time.com: Video: Understanding the Heart Hazards of Marathon Running)
“The frequency of the physical activity is a big deal here,” says Nieman. “You can’t be a weekend warrior and expect these effects.” Which means that if you want to avoid a cold this season, you’re going to have to work for it.
More on Time.com: