Don’t fret. Improving your breathing is relatively easy. To train himself to stop breathing through his mouth, Nestor simply stuck a small piece of surgical tape across his lips at night.

I wore my mouth tape every night for three weeks, and once I’d gotten over the guilt about single-use products going straight ...

What can you do to fix it? When Nestor blocked his nose for science, he experienced an extreme version of mouth breathing.

Experts agree there are benefits to slower breathing and keeping your mouth closed: breathing entirely through your nose.

California native James Nestor suggests that breathing correctly and efficiently could potentially prevent a host of chronic illnesses and conditions.

Closing your mouth and breathing through your nose can improve sleep, too. "Nasal breathing has a profound effect on sleep quality, oxygenation, and relaxation," Nestor says.

To calculate how mouth breathing affected the body and mind, Nestor measured physiological data three times a day. Courtesy James Nestor ...