Evidence from sports docs found that people who work out at least 5 days a week — whether they’re 18 or 85 — get half as many fall/winter colds as those who work up a sweat only once a week, if ever. And when they do catch colds, they have milder symptoms and fewer sick days. One of these a day keeps a cold away.
So along with lifting your mood, firming your belly, and strengthening your heart, being active also seems to increase the immune cells circulating in your body.