There's even more evidence that one type of exercise is the closest thing to a miracle drug that we have

• Aerobic exercise provides a ton of benefits, from a lift in mood to more toned muscles.
• Some of the benefits can emerge within minutes, while others might take several days or weeks to crop up.
• A new study suggests that aerobic exercise also changes the makeup of the microbes in our gut.

Aerobic exercise, or "cardio," might be the closest thing to a miracle drug that we have.

When we commit to regular workouts that raise our heart rate and get us moving and sweating for a sustained period of time, magical things happen to our mind and body. We start to think more clearly, feel better about ourselves, and even build buffers against age-related cognitive decline. Our lungs and heart get stronger, too.

But cardio may have other less obvious benefits as well. A small study published in November suggests that activities like walking, swimming, and running - while they are no short-cut to weight loss - also change the makeup of the microbes in our gut. These microbes play a role in everything from our energy levels to inflammation, a key early warning sign of illness.

"These are the first studies to show that exercise can have an effect on your gut independent of diet or other factors," Jeffrey Woods, a University of Illinois professor of kinesio logy and community health who led the research, said in a statement.

That could have important implications for learning more about why exercise seems to be so uniquely capable of lifting our spirits and energizing our bodies.

Cardio impacts our gut - but not in the way you might think

For the most recent study, published in the journal Medicine & Science in Sports Exercise, Woods and a team of other scientists looked at 32 lean and obese women who had been essentially inactive before the study. For six weeks, three days each week, the participants either cycled, walked or ran on a treadmill, or used an elliptical machine. They started with a moderate 30-minute workout and worked up to a vigorous one-hour burst by the time the study finished.

"They had a choice of activity on any given day, but most chose the treadmill," Woods told Business Insider.

After their six-week workout regimen ended, the participants were instructed to go back to their normal sedentary lifestyles for another month and a half.

The researchers looked at the microbes in participants' guts using fecal samples immediately after their exercise program, and then again after six weeks of not working out. They found that after weeks of exercise, people's concentrations of butyrate - a special type of fatty acid that helps keep our guts happy by tamping down on inflammation and producing energy - went up. These concentrations soared in the lean participants, and picked up modestly among those in the obese group.

"The bottom line is that there are clear differences in how the microbiome of somebody who is obese versus somebody who is lean responds to exercise," Woods said. "We have more work to do to determine why that is."

How aerobic workouts clear the mind and lift our mood

Precisely how cardio affects different types of bodies remains somewhat murky. But its powerful ability to clear the mind has been well documented by a handful of recent studies.

"Aerobic exercise ... has a unique capacity to exhilarate and relax, to provide stimulation and calm, to counter depression and dissipate stress," the authors of an article in the Harvard Medical School blog "Mind and Mood" wrote.

Some of cardio's benefits - like a lift in mood - can emerge as soon as a few minutes into a sweaty bike ride, while others - like improved memory - might take several weeks to crop up.

The reason aerobic workouts seem to lift our spirits seems related to its ability to reduce levels of natural stress hormones, such as adrenaline and cortisol, according to a recent study in the Journal of Physical Therapy Science. Activities like running and swimming also increase overall blood flow and provide our minds with fresh energy and oxygen - another factor that could help us feel better.

Those benefits may be one of the reasons that working out is so helpful for people with depression. A pilot study in people with severe depression found that just 30 minutes of treadmill walking for 10 consecutive days was "sufficient to produce a clinically relevant and statistically significant reduction in depression."

But the mental benefits of heart-pumping workouts aren't confined to better moods. This kind of exercise also seems to improve our memory and may even guard against some of the detrimental effects of aging. Those boons suggest cardio may help defend the brain against physical changes that come with age.

A study published in May found that in adults aged 60-88, walking for 30 minutes four days a week for 12 weeks appeared to strengthen connectivity in a region of the brain where weakened connections have been linked with memory loss. And a recent study in older women who displayed potential symptoms of dementia found that aerobic exercise was linked with an increase in the size of the hippocampus, a brain area involved in learning and memory.

If you're over 50, a study in the British Medical Journal suggests the best results come from combining aerobic and resistance exercise, which could include anything from high-intensity interval training, like the 7-minute workout, to dynamic flow yoga, which intersperses strength-building poses like planks and push-ups with heart-pumping dance-like moves.

So what are you waiting for? Get moving, and keep it up.